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melanism industri, gelap-pada kulit, bulu, atau bulu-diakuisisi oleh populasi binatang yang hidup di sebuah kawasan industri di mana lingkungan ber jelaga gelap. melanisasi dari populasi meningkatkan kemungkinan bahwa organisme akan bertahan hidup dan bereproduksi; itu berlangsung selama beberapa generasi sebagai hasil dari seleksi alam, dari hewan yang lebih mencolok oleh predator.
Dari awal beberapa penyebab telah diusulkan untuk perubahan frekuensi gen melanic di ngengat peppered Biston betularia dan ngengat melanic industri lainnya. Hal ini termasuk intrinsik yang lebih tinggi dari bentuk melanic dan predasi selektif untuk kamuflase. metode baru analisis harus memberikan informasi lebih lanjut tentang sistem melanic dan migrasi yang akan melengkapi pemahaman kita tentang contoh penting dari evolusi cepat.
TYPES OF INDUSTRIAL MELANISM
Three categories of industrial
melanism have been recognized:
Melanin adalah pigmen gelap yang bertanggung jawab untuk proses penyamakan yang terjadi pada manusia ketika mereka terkena sinar matahari. Pada orang sebenarnya merupakan reaksi terhadap kerusakan sel-sel kulit. hewan melanistic memiliki peningkatan jumlah pigmentasi hitam atau hampir hitam di kulit, bulu, rambut, atau jaringan luar lainnya. Melanism adalah kebalikan dari albinisme dan terjadi dengan sekitar frekuensi yang sama.
Dermal melanin diproduksi oleh sel-sel kulit yang disebut melanosit. Manusia umumnya memiliki konsentrasi yang sama dari melanosit di kulit mereka. Namun, melanosit pada beberapa individu atau kelompok etnis mengekspresikan melanin memproduksi gen lebih atau kurang sering mengakibatkan konsentrasi yang lebih besar atau lebih kecil dari melanin kulit.
Albinisme melanism albinisme Disebabkan oleh kekurangan melanin
. Namun, populasi gelap (melanic) tikus ditemukan pada lava gelap, dan warna menyembunyikan ini memberikan perlindungan dari predator burung dan mamalia.
Morph melanistic benar-benar warna morph pertama dan morph warna paling klasik dari Thamnophis.
Melanism adalah bentuk warna di mana individu memiliki jumlah abnormal pigmen hitam. dasar genetik yang tidak dipahami dengan baik, tetapi perkawinan sedarah dianggap bagian dari penyebabnya.
Dua makalah baru-baru ini atas dasar molekul melanism memperkuat rantai bukti yang menghubungkan genotipe dan fenotipe di alam.
Melanism related to the process of adaptation is called adaptive. Most commonly, dark
individuals become fitter to survive and reproduce in their
environment as they are better camouflaged. This makes some species less
conspicuous to predators, while others, such as black panthers, use it as a foraging advantage during
night hunting.[6] Typically, adaptive melanism is heritable: A dominant gene,
which is entirely or nearly entirely expressed in the phenotype, is responsible for the excessive
amount of melanin.
Melanism terkait dengan proses adaptasi yang
disebut adaptif. Paling umum, individu berwarna gelap menjadi bertahan untuk bertahan hidup dan bereproduksi di
lingkungan mereka karena mereka disamarkan dengan lebih baik. Hal ini membuat
beberapa spesies kurang mencolok bagi predator, sementara yang lain, seperti
kumbang hitam, menggunakannya sebagai keuntungan mencari makan selama berburu
malam. Biasanya, melanism adaptif adalah diwariskan: merupakan sebuah gen dominan, yang seluruhnya atau hampir seluruhnya dalam
phenotype, bertanggung jawab untuk jumlah melanin yang berlebihan .
Melanism is a development of the dark-colored pigment melanin in the skin or its appendages and is the opposite
ofalbinism. Historically, it was also the medical term for black jaundice.[2]
Melanism merupakan pengembangan dari
pigmen melanin berwarna gelap pada kulit atau pelengkap dan berlawanan dengan
albinism . Kata melanism berasal dari bahasa Yunani:. Μελανός ( "pigmen
hitam")
Pseudo-melanism, also called abundism, is another variant of
pigmentation, characterized by dark spots or enlarged stripes, which cover a
large part of the body of the animal, making it appear melanistic.[4] A deficiency in or total absence of melanin
pigments is called amelanism
Pseudo-Melanisme, juga disebut abundism,
adalah varian lain dari pigmentasi, yang ditandai dengan bintik-bintik gelap
atau garis-garis yang diperbesar, yang menutupi sebagian besar tubuh hewan,
sehingga tampak melanistic. Kekurangan
atau total ketiadaan pigmen melanin disebut amelanism
Industrial
melanism is an effect of urban pollution prominent in many species of
arthropods. It is the phenomenon of an organism evolving dark pigmentation when
exposed to an environment polluted by dark soot deposit and sulfuric buildup
from industrial pollution. In this type of industrial melanism, the darker
pigmented individuals develop a higher fitness and are favored by natural
selection. This change in favoritism as a result of modification in selection
pressure is one of the best-noted cases of Darwinian evolution.[8] The most common case of this adaptation is found in the arthropod order Lepidoptera.
melanism industrial adalah efek dari polusi perkotaan di banyak
spesies arthropoda. Ini adalah fenomena organisme berkembangnya pigmentasi gelap saat terkena lingkungan
tercemar oleh deposito jelaga gelap dan penumpukan sulfat dari polusi industri.
Dalam jenis melanism industrial ini ,
individu berpigmen gelap mengembangkan pertahanan yang lebih tinggi dan disukai oleh seleksi
alam. Perubahan ini sebagai akibat dari modifikasi tekanan seleksi yang
merupakan salah satu kasus yang paling
mencatat pada evolusi Darwin. Kasus yang paling umum dari adaptasi ini
ditemukan dalam urutan arthropoda Lepidoptera.
Melanistic
animals were found to carry at least one copy of a mutant MC1R sequence allele, bearing a 15-base pair inframe deletion.
hewan melanistic ditemukan untuk membawa
setidaknya satu salinan dari urutan MC1R alel mutan, bearing 15-base pair
inframe deletion.
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Melanism is an undue development
of dark-colored pigment in the skin or its appendages and is the opposite of
albinism. The word ‘melanism’ is deduced from a Greek word that means black
pigment. Pseudo-melanism, also called abundism, is another variant of
pigmentation, characterized by dark spots or enlarged stripes, which cover a
large part of the body of the animal making it appear melanistic.
Melanism related to the process of adaptation is
called adaptive.
Melanism merupakan perkembangan yang tidak semestinya dari pigmen berwarna gelap di kulit atau pelengkap dan merupakan kebalikan dari albinisme. Kata 'melanism' disimpulkan dari kata Yunani yang berarti pigmen hitam. Pseudo-Melanisme, juga disebut abundism, adalah varian lain dari pigmentasi, yang ditandai dengan bintik-bintik gelap atau garis-garis diperbesar, yang menutupi sebagian besar tubuh hewan sehingga tampak melanistic.
Melanism terkait dengan proses adaptasi disebut adaptif.
.............................
Industrial melanism
industrial melanism, the darkness—of the skin, feathers, or
fur—acquired by a population of animals living in an industrial region where
the environment is soot-darkened. The melanization of a
population increases the probability that its members will survive and
reproduce; it takes place over the course of many generations as the result of natural selection of the lighter, more conspicuous
animals by predators.
melanism industri, gelap-pada kulit, bulu, atau bulu-diakuisisi oleh populasi binatang yang hidup di sebuah kawasan industri di mana lingkungan ber jelaga gelap. melanisasi dari populasi meningkatkan kemungkinan bahwa organisme akan bertahan hidup dan bereproduksi; itu berlangsung selama beberapa generasi sebagai hasil dari seleksi alam, dari hewan yang lebih mencolok oleh predator.
........................
From
the outset multiple causes have been suggested for changes in melanic gene
frequency in the peppered moth Biston betularia and other industrial melanic moths. These have included higher
intrinsic fitness of melanic forms and selective predation for camouflage.
New
methods of analysis should supply further information on the melanic system and
on migration that will complete our understanding of this important example of
rapid evolution.
Dari awal beberapa penyebab telah diusulkan untuk perubahan frekuensi gen melanic di ngengat peppered Biston betularia dan ngengat melanic industri lainnya. Hal ini termasuk intrinsik yang lebih tinggi dari bentuk melanic dan predasi selektif untuk kamuflase. metode baru analisis harus memberikan informasi lebih lanjut tentang sistem melanic dan migrasi yang akan melengkapi pemahaman kita tentang contoh penting dari evolusi cepat.
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The
darker variant, on the other hand, was now camouflaged, and more likely to
survive and breed. In a textbook case of industrial melanism , in just a few
generations, the dark variant became by far the most common.
In just over 50 years, the dark variety went from making up just 2% of
the population to making up over 95%, a change that could not be explained by
any theory other than natural selection and industrial melanism.
The incidence of industrial melanism is a process called
micro-evolution, where selection pressures within a species lead to changes.
Varian gelap, di sisi lain, sekarang disamarkan, dan lebih mungkin untuk bertahan hidup dan berkembang biak. Dalam kasus buku teks melanism industri, hanya dalam beberapa generasi, varian gelap menjadi yang paling umum.
Dalam lebih dari 50 tahun, berbagai variasi gelap naik hanya 2% dari populasi untuk membentuk lebih dari 95%, perubahan yang tidak bisa dijelaskan dengan teori selain seleksi alam dan melanism industri.
Insiden melanism industri adalah proses yang disebut micro-evolusi, di mana tekanan seleksi dalam spesies menyebabkan perubahan.
...............................
Industrial melanism may be defined as a
proportional increase of dark, or melanin, pigments in individuals of a
population, caused by changes in the environment resulting from industrial
pollution.
melanism industri dapat didefinisikan sebagai peningkatan proporsional gelap, atau melanin, pigmen pada individu dari suatu populasi, yang disebabkan oleh perubahan lingkungan yang dihasilkan dari polusi industri.
TYPES OF INDUSTRIAL MELANISM
Three categories of industrial
melanism have been recognized:
A. Full industrial melanic polymorphism involves distinct
melanic forms that have arisen since the industrial revolution and have
increased as a consequence of the effects of industrialization on the
environment.
B. Partial industrial melanic polymorphism involves polymorphic species that had distinct melanic forms prior to the industrial revolution.
These forms have increased in frequency following and as a consequence of the effects of industrialization.
B. Partial industrial melanic polymorphism involves polymorphic species that had distinct melanic forms prior to the industrial revolution.
These forms have increased in frequency following and as a consequence of the effects of industrialization.
C. Polygenic industrial melanism involves species in
which the average ground color of some or all members of a population has
darkened gradually as a consequence of the effects of industrialization.
It should be noted that melanism is a common phenomenon throughout the animal kingdom, with many factors unrelated to industrialization or pollution influencing the success of melanic forms in some species, including humans.
It should be noted that melanism is a common phenomenon throughout the animal kingdom, with many factors unrelated to industrialization or pollution influencing the success of melanic forms in some species, including humans.
JENIS INDUSTRI melanism
Tiga kategori melanism industri :
A. industri penuh polimorfisme melanic melibatkan bentuk melanic berbeda yang telah muncul sejak revolusi industri dan telah meningkat sebagai konsekuensi dari efek industrialisasi terhadap lingkungan.
B. Partial industri polimorfisme melanic melibatkan spesies polimorfik yang memiliki bentuk melanic yang berbeda sebelum revolusi industri.
Bentuk-bentuk telah meningkat dalam frekuensi sebagai konsekuensi dari efek industrialisasi.
C. poligenik melanism industri melibatkan spesies di mana warna tanah beberapa atau semua anggota populasi telah gelap secara bertahap sebagai akibat dari efek industrialisasi.
Perlu dicatat bahwa melanism adalah fenomena umum di seluruh kerajaan hewan, dengan banyak faktor yang tidak terkait dengan industrialisasi atau polusi mempengaruhi keberhasilan bentuk melanic di beberapa spesies, termasuk manusia.
........................
J jaguar melanistic pada Henry
Doorly Zoo. Melanism adalah hasil dari sebuah alel dominan tetapi
tetap relatif langka di jaguar.
..................................
Mungkin dari kita semua
jarang mendengar kata ini. Melanistic adalah kelainan kulit, yang bertolak
belakang dengan Albino, namun hewan hewan Melanistic pun sangatlah
menawan
................................
Melanisme
merupakan perkembangan yang tidak semestinya dari pigmen warna gelap di kulit
dan merupakan kebalikan dari albinisme. 'Melanisme' berasal dari kata Yunani
yang berarti pigmen hitam. Pseudo-Melanisme, juga disebutabundism, merupakan
varian dari pigmentasi, yang ditandai dengan bintik hitam atau garis yang
diperbesar, yang menutupi sebagian besar tubuh hewan sehingga tampak
melanistic.
Melanisme yang terkait dengan proses adaptasi
disebut adaptif.
Paling umum, individu gelap menjadi lebih bisa bertahan hidup dan bereproduksi
dalam lingkungan mereka karena mereka disamarkan dengan lebih baik. Hal ini
membuat beberapa spesies kurang mencolok atau terlindung dari predator,
Biasanya Melanisme adaptif adalah diwariskan:
Sebuah gen dominan, yang seluruhnya atau hampir seluruhnya dalam phenotype
bertanggung jawab atas jumlah berlebihan melanin. Melanisme Adaptif telah
terbukti terjadi dalam berbagai hewan, termasuk mamalia seperti tupai, kucing,
dan ular karang.
.............................
Melanism industri adalah istilah
biologi mengacu pada hewan. Itu berarti merujuk penggelapan dari kulit atau
yang di tempatnya seperti bulu
..................
The increased development of the
dark-colored pigment melanin in the skin and hair of an
animal is called Melanism, and is the opposite of Albinism. Just like
Albinism results in stunningly
white animals, Melanism can create all-black animals
Perkembangan yang meningkat dari melanin pigmen berwarna gelap di kulit dan rambut binatang disebut melanism, dan merupakan kebalikan dari Albinisme. Sama seperti hasil Albinisme pada hewan yang memukau putih, melanism dapat membuat hewan semua hitam
.......................
Melanin is the dark pigmentation
which is responsible for the tanning process which occurs in humans when
they're exposed to sunlight. In people it is actually a reaction to damage
of the skin cells. A melanistic animal has an increased amount of this black or
nearly black pigmentation in the skin, feathers, hair, or other outer tissues.
Melanism is
the opposite of albinism and occurs with about the same frequency.
Melanin adalah pigmen gelap yang bertanggung jawab untuk proses penyamakan yang terjadi pada manusia ketika mereka terkena sinar matahari. Pada orang sebenarnya merupakan reaksi terhadap kerusakan sel-sel kulit. hewan melanistic memiliki peningkatan jumlah pigmentasi hitam atau hampir hitam di kulit, bulu, rambut, atau jaringan luar lainnya. Melanism adalah kebalikan dari albinisme dan terjadi dengan sekitar frekuensi yang sama.
...............................
Usually,
melanism is defined by the increase of dark pigmentation present in an
organism.
Melanism
is a genetic variation that causes an animal to have too much pigmentation.
This is a phenomenon that has been observed in many species from the animal
kingdom.
Biasanya, melanism didefinisikan oleh kenaikan hadirnya pigmentasi gelap pada sebuah organisme.
Melanism adalah variasi genetik yang menyebabkan hewan untuk memiliki terlalu banyak pigmentasi. Ini adalah fenomena yang telah diamati pada banyak spesies dari hewan.
........................
In
the noctuid moth Panthea furcilla (Packard) melanism is increasing rapidly in
Putnam, Connecticut, an area not subject to appreciable industrial pollution.
Wholly melanic and very strongly melanistic are dominant over normal gray, and
wholly melanic is dominant over very strongly melanistic. Larval melanism is
independent of adult melanism.’
Dalam ngengat noctuid Panthea furcilla (Packard) melanism meningkat dengan cepat di Putnam, Connecticut, Sepenuhnya melanic dan melanistic sangat kuat yang dominan atas abu-abu normal, dan sepenuhnya melanic dominan atas sangat kuat melanistic yang sangat kuat . melanism larva independen dari melanism dewasa.
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Melanistic adalah istilah yang digunakan untuk
harimau yang kelebihan pigmen, ini adalah kebalikan dari ablonisium yang tidak
memiliki pigmen. Harimau melanistic hampir semua hitam dengan garis-garis
kuning jeruk terutama pada bagian bawahnya.
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Melanistic (black beauties)
Ketika ada kelainan dimana pigmen
warna melanin kekurangan, yang disebut albino, maka ada pula yang memiliki
kelebihan gen warna hitam ini, disebut sebagai black beauties
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Melanic
(darkly pigmented) phenotypes in mammals provide a potent system in which to
study the genetic basis of naturally occurring mutant phenotypes because
melanism occurs in many mammals, and the mammalian pigmentation pathway is well
understood
Melanic (berpigmen gelap) fenotipe pada mamalia menyediakan sistem ampuh di mana untuk belajar dasar genetik yang terjadi secara alami fenotipe mutan karena melanism terjadi di banyak mamalia, dan pigmentasi jalur mamalia dipahami dengan baik
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Dermal melanin is produced by skin cells called
melanocytes. Humans generally possess a similar concentration of
melanocytes in their skin. However, melanocytes in some individuals or
ethnic groups express the melanin producing gene more or less frequently
resulting in a greater or lesser concentration of skin melanin.
Dermal melanin diproduksi oleh sel-sel kulit yang disebut melanosit. Manusia umumnya memiliki konsentrasi yang sama dari melanosit di kulit mereka. Namun, melanosit pada beberapa individu atau kelompok etnis mengekspresikan melanin memproduksi gen lebih atau kurang sering mengakibatkan konsentrasi yang lebih besar atau lebih kecil dari melanin kulit.
..........................
Albinism Melanism Albinism Caused by a
deficiency of melanin
Albinisme melanism albinisme Disebabkan oleh kekurangan melanin
........................
Melanistic
coat coloration occurs as a common polymorphism in 11 of 37 felid species and
reaches high population frequency in some cases but never achieves complete
fixation
Melanistic warna mantel terjadi sebagai polimorfisme umum di 11 dari 37 spesies felid dan mencapai frekuensi populasi yang tinggi dalam beberapa kasus tetapi tidak pernah mencapai fiksasi lengkap
...........................
. However, populations of dark (melanic) mice are found on dark
lava, and this concealing coloration provides protection from avian and
mammalian predators.
. Namun, populasi gelap (melanic) tikus ditemukan pada lava gelap, dan warna menyembunyikan ini memberikan perlindungan dari predator burung dan mamalia.
.......................
In jaguars and
jaguarundis, dark pigment is linked to two different mutations in the same
gene, MC1R. MC1R belongs to a family of genes that
code for proteins called (seven-helix) transmembrane receptors that stud the
surface of cells.
Dalam jaguar dan jaguarundi, pigmen gelap terkait dengan dua mutasi yang berbeda pada gen yang sama, MC1R. MC1R milik keluarga gen dimana kode untuk protein yang disebut (tujuh helix) reseptor transmembran permukaan sel.
...............................
Melanictic adalah semua
warna hewan berwarna hitam, kebalikannya dari jenis albino yang bisa terjadi di
alam
.............................
Melanophores: produce black pigment (melanin).
.............................
Semua
orang pasti sudah tahu tentang Albino yaitu kelainan pigmen yang menyebabkan
sekujur tubuh pengidap kelihatan putih. Namun bagaimana dengan dengan
Melanisme?
Melanisme bisa dibilang lawan dari Albino, jika penderita kelihatan Putih maka kebalikannya penderita Melanisme kelihatan sangat hitam.
Kata 'Melanisme' berasal dari bahasa Yunani : μελανός , yang berarti pigmen hitam. Penyakit Melanisme merupakan perkembangan pigmen hitam yang pesat sehingga tubuh kelihatan sangat hitam.
Melanisme bisa dibilang lawan dari Albino, jika penderita kelihatan Putih maka kebalikannya penderita Melanisme kelihatan sangat hitam.
Kata 'Melanisme' berasal dari bahasa Yunani : μελανός , yang berarti pigmen hitam. Penyakit Melanisme merupakan perkembangan pigmen hitam yang pesat sehingga tubuh kelihatan sangat hitam.
Melanisme atau melanosis pada manusia terjadi di organ
tertentu. Misalnya, melanosis coli mengacu pada peningkatan pigmentasi pada
lapisan usus besar. Ini sebenarnya karena penggunaan berlebihan obat pencahar
dan merupakan sedikit keliru karena tidak disebabkan meningkatnya pigmen
melanin, melainkan, lipofuscin dalam makrofag.
Melanisme terkait dengan proses adaptasi disebut adaptif.
Paling umum, individu gelap menjadi bugar untuk bertahan hidup dan bereproduksi
dalam lingkungan mereka karena mereka disamarkan baik. Hal ini membuat beberapa
spesies predator kurang mencolok, sementara yang lain seperti macan kumbang
hitam menggunakannya sebagai keuntungan berburu mencari makan pada malam hari.
.................................
The melanistic morph is truly the first and
most classic color morph of
Thamnophis.
Morph melanistic benar-benar warna morph pertama dan morph warna paling klasik dari Thamnophis.
..............................
Melanism is a colour form in which
individuals have abnormal amounts of black pigment. Its genetic basis is not
well understood, but inbreeding is thought to be part of the cause.
Melanism adalah bentuk warna di mana individu memiliki jumlah abnormal pigmen hitam. dasar genetik yang tidak dipahami dengan baik, tetapi perkawinan sedarah dianggap bagian dari penyebabnya.
........................................
melanism. Melanism is essentially the
opposite of albinism
melanism is the overabundance of
melanin, leading to an individual with an abnormal amount of black coloration.
Melanistic Eastern Garter Snakes can be found along the Western Basin of Lake
Erie and on some of the Lake Erie Islands. Some populations can be up to 50%
melanistic in this area, meaning there will be a mixture of normal-looking and
melanistic individuals within one area.
melanism. Melanism dasarnya kebalikan dari albinisme
melanism adalah hal mekanin yang meluap-luap , menyebabkan seorang individu dengan jumlah abnormal warna hitam. Melanistic ular garter Timur dapat ditemukan di sepanjang Barat Basin Danau Erie dan pada beberapa Lake Erie Islands. Beberapa populasi bisa sampai 50% melanistic di daerah ini, yang berarti akan ada campuran individu normal dan melanistic dalam satu wilayah.
.................................
Despite
extensive research, the function and adaptive significance of melanism remain
controversial.In snakes, melanistic individuals enjoy a thermal advantage
compared with normal-colored individuals due to superior thermoregulatory
capabilities. The hypothetical consequences of this thermal advantage are that
melanistic individuals have longer daily and seasonal active periods, and thus
collect more food, resulting in a higher growth rate and larger body size.
Meskipun penelitian yang luas, fungsi dan signifikansi adaptif dari melanism tetap controversial.pada ular, individu melanistic menikmati keuntungan termal dibandingkan dengan individu normal berwarna karena kemampuan termoregulasi superior. Konsekuensi hipotetis keunggulan thermal ini adalah bahwa individu melanistic memiliki periode hari yang lebih panjang dan periode aktif musiman, dan dengan demikian dapat mengumpulkan lebih banyak makanan, sehingga membuat tingkat pertumbuhan yang lebih tinggi dan ukuran tubuh yang lebih besar.
...............................
Melanistic garter snakes (Thamnophis sirtalis) are unusually common near Lake Erie, apparently because selection for thermoregulatory ability in cool lake-shore habitats (which favours melanistic morphs) outweighs selection for crypsis (which favours striped morphs).
ular garter melanistic (sirtalis Thamnophis) yang biasa umum di dekat Danau Erie, rupanya karena seleksi untuk kemampuan termoregulasi di habitat danau-shore yang dingin (yang morphs melanistic) melebihi seleksi untuk crypsis (yang morphs bergaris).
.......................................
Neuronal pigments of melanic type were identified in the
putamen, cortex, cerebellum, and other major regions of human brain. These
pigments consist of granules 30 nm in size, contained in organelles together
with lipid droplets, and they accumulate in aging, reaching concentrations as
high as 1.5–2.6 μg/mg tissue in major brain regions. These pigments, which we
term neuromelanins, contain melanic, lipid, and peptide components.
pigmen neuronal tipe melanic diidentifikasi dalam putamen, korteks, serebelum, dan daerah besar lainnya dari otak manusia. Pigmen ini terdiri dari butiran 30 nm dalam ukuran, yang terkandung dalam organel bersama-sama dengan tetesan lipid, dan mereka terakumulasi dalam penuaan, mencapai konsentrasi setinggi 1,5-2,6 mg / mg jaringan di daerah otak besar. pigmen ini, yang neuromelanins, mengandung komponen melanic, lipid, dan peptida.
.................................
melanin, a dark biological pigment (biochrome) found in skin, hair,
feathers, scales, eyes, and some internal membranes; it is also found in the
peritoneum of many animals (e.g., frogs),
Melanism
refers to the deposition of melanin in the tissues of living animals. The
chemistry of the process depends on the metabolism of the amino acid tyrosine, the absence of which results in albinism, or lack of pigmentation.
“Industrial” melanism has occurred in certain moth
populations, in which the predominant coloration has
changed pale gray to dark-coloured individuals.
melanin, pigmen biologi gelap (biochrome) ditemukan di kulit, rambut, bulu, sisik, mata, dan beberapa membran internal, itu juga ditemukan dalam peritoneum di banyak hewan (misalnya, katak),
Melanism mengacu pada deposisi melanin dalam jaringan hewan hidup. Prose Kimia tergantung pada metabolisme asam amino tirosin, tidak adanya yang menyebabkan albinisme, atau kurangnya pigmentasi.
"Industri" melanism telah terjadi pada populasi ngengat tertentu, di mana warna dominan telah berubah pucat abu-abu untuk individu berwarna gelap
...............................................
The
present study sought to determine whether the pigment produced by Proteus
mirabilis from the L-forms of various aromatic amino acids under aerobic
conditions is melanic in nature. It is a black-brown pigment which behaves like
a melanin in many respects, namely solubility features, bleaching by oxidizing
agents and positive response to the Fontana-Masson assay.
Penelitian ini berusaha untuk menentukan apakah pigmen yang dihasilkan oleh Proteus mirabilis dari bentuk-L berbagai asam amino aromatik di bawah kondisi aerobik adalah melanic di alam. Ini adalah pigmen hitam-coklat yang berperilaku seperti melanin dalam banyak hal, yaitu fitur kelarutan, pemutihan oleh agen pengoksidasi dan respon positif terhadap uji Fontana-Masson.
......................................
The dark brown pigments derived from
tea and tea polyphenols were studied. Physical and chemical properties revealed
that pigments directly extracted from tea leaves and derived from tea
polyphenols were similar to typical melanins. Further investigation showed that
both melanic pigments possessed similar antioxidant capability, due to their
chelating and scavenging properties.
Pigmen coklat gelap yang berasal dari teh dan teh polifenol dipelajari. sifat fisik dan kimia mengungkapkan bahwa pigmen langsung diekstrak dari daun teh dan berasal dari polifenol teh yang mirip dengan melanins yang khas. Penyelidikan lebih lanjut menunjukkan bahwa kedua pigmen melanic dimiliki kemampuan antioksidan yang sama, karena kelat dan pembilasan sifat mereka.
.................................
Mimicry and melanism in Lepidoptera provided the first
convincing examples of natural selection in action. Genetic analysis has now
shown that, surprisingly, mimicry in Heliconius butterflies and melanism in peppered
moths are switched at precisely the same gene: cortex.
Mimikri dan melanism di Lepidoptera memberikan contoh meyakinkan pertama dari seleksi alam dalam tindakan. Analisis genetik kini telah menunjukkan bahwa, secara mengejutkan, mimikri di kupu-kupu Heliconius dan melanism pada ngengat diaktifkan tepat pada gen yang sama: korteks.
..............................
MC1R, also known as the extension gene,
controls production of pigment in melanocytes. The dominant form of the gene,
the "E" allele, allows the dog to produce eumelanin, which is a black
pigment. A mutation in the MC1R gene causes the pigment-producing cells to only
produce phaeomelanin, turning all eumelanin in the coat to phaeomelanin. This
form of the gene is represented as the "e" allele. The "e"
allele is recessive, meaning that a dog must have two copies of the MC1R
mutation to express the yellow or red coat color. Recessive red can mask other
color variants even masking merle.
MC1R, juga dikenal sebagai gen ekstensi, mengontrol produksi pigmen pada melanosit. Bentuk dominan dari gen, "E" alel, memungkinkan anjing untuk menghasilkan eumelanin, yang merupakan pigmen hitam. Sebuah mutasi dalam gen MC1R menyebabkan sel penghasil pigmen hanya menghasilkan phaeomelanin, mengubah semua eumelanin dalam mantel untuk phaeomelanin. Bentuk gen diwakili sebagai "e" alel. "E" alel resesif, yang berarti bahwa anjing harus memiliki dua salinan dari mutasi MC1R untuk mengekspresikan warna bulu kuning atau merah. merah resesif dapat menutupi varian warna lain bahkan masking Merle.
....................................
Industrial
melanism refers to the evolution of dark body colours in animal species that
live in habitats blackened by industrial soot. The phenomenon has been
documented in numerous species that hide from predators by blending in with
their backgrounds. Peppered moths provide one example. Before the industrial
revolution, peppered moths in the UK were pale grey, but after their habitats
became polluted with soot from coal‐fired industries, melanic
(black) phenotypes became numerous and spread to other regions
melanism industri mengacu pada evolusi warna tubuh gelap spesies hewan yang hidup di habitat menghitam oleh jelaga industri. Fenomena ini telah didokumentasikan dalam banyak spesies yang bersembunyi dari predator dengan membaur dengan latar belakang mereka. ngengat memberikan salah satu contoh. Sebelum revolusi industri, ngengat di Inggris abu-abu pucat, tapi setelah habitatnya menjadi tercemar dengan jelaga dari industri batu bara, fenotipe melanic (hitam) menjadi banyak dan menyebar ke daerah lain
............................
Morphological variation in natural
populations is a genomic test bed for studying the interface between molecular
evolution and population genetics, but some of the most interesting questions
involve non-model organisms that lack well annotated reference genomes. Many
felid species exhibit polymorphism for melanism but the relative roles played
by genetic drift, natural selection, and interspecies hybridization remain uncertain.
variasi morfologi dalam populasi alami adalah test bed genom untuk mempelajari antarmuka antara molekul evolusi dan populasi genetika, tetapi beberapa pertanyaan yang paling menarik melibatkan organisme non-model yang referensi genom dijelaskan kurang baik . Banyak felid polimorfisme spesies exhibit untuk melanism tetapi peran relatif dimainkan oleh hanyutan genetika, seleksi alam, dan antar spesies hibridisasi tetap tidak menentu.
..........................
The occurrence of melanism (darkening
of the background coloration) is documented in 13 felid species, in some cases
reaching high frequencies at the population level.
Terjadinya melanism (gelap dari warna latar belakang) didokumentasikan dalam 13 spesies felid, dalam beberapa kasus mencapai frekuensi tinggi pada tingkat populasi.
..........................
Two
recent papers on the molecular basis of melanism strengthen the chain of
evidence linking genotype and phenotype in nature.
Dua makalah baru-baru ini atas dasar molekul melanism memperkuat rantai bukti yang menghubungkan genotipe dan fenotipe di alam.
........................
.....................................................................
Melanism
Melanism
From Wikipedia, the free encyclopedia
Melanism is a development of the dark-colored pigment melanin in the skin or its appendages and is the opposite
ofalbinism. Historically, it was also the medical term for black jaundice.[2]
Pseudo-melanism, also called abundism, is another variant of pigmentation,
characterized by dark spots or enlarged stripes, which cover a large part of
the body of the animal, making it appear melanistic.[4] A deficiency in or total absence of melanin
pigments is called amelanism.
The morbid deposition of black
matter, often of a malignant character causing pigmented tumors, is called melanosis.[5] For a description of melanin-related
disorders, see melanin, melanosis
coli and ocular
melanosis.
Adaptation[edit]
Melanism related to the process of adaptation is called adaptive. Most commonly, dark
individuals become fitter to survive and reproduce in their
environment as they are better camouflaged. This makes some species less
conspicuous to predators, while others, such as black panthers, use it as a foraging advantage during
night hunting.[6] Typically, adaptive melanism is heritable: A dominant gene,
which is entirely or nearly entirely expressed in the phenotype, is responsible for the excessive
amount of melanin.
Adaptive melanism has been
shown to occur in a variety of animals, including mammals such as squirrels, many felines andcanids, and coral snakes.
Adaptive melanism can lead to the creation of morphs, the most notable example being thepeppered
moth, whose evolutionary history in the United
Kingdom is
offered as a classic instructional tool for teaching the principles of natural
selection.[7]
Industrial Melanism[edit]
Industrial melanism is an effect of urban pollution prominent in many
species of arthropods. It is the phenomenon of an organism evolving dark
pigmentation when exposed to an environment polluted by dark soot deposit and
sulfuric buildup from industrial pollution. In this type of industrial
melanism, the darker pigmented individuals develop a higher fitness and are
favored by natural selection. This change in favoritism as a result of
modification in selection pressure is one of the best-noted cases of Darwinian
evolution.[8] The most common case of this adaptation
is found in the arthropod order Lepidoptera. This order of insects
encompasses all insects with microscopic scales on their wings, such as moths
and butterflies. Some species thought to undergo the selection of industrial
melanism are Adalia
bipunctata (two-spot
ladybird), Hamadryas
feronia(variable cracker butterfly), Odontopera bidentata (scalloped hazel moth), Oligia
latruncula (tawny
marbled minor moth),Oligia
strigilis (marbled
minor moth), and many other species of moths; but probably the best and most
studied example of industrial melanism is in the peppered moth, Biston
betularia. Originally, peppered moths lived where light-colored lichens
covered the trees where they would rest. To camouflage with the tree, they
originated with a light-colored pigment that helped them to avoid predators by
not being a visual distraction. Lichens are great bio-indicators of
air-pollution.[9] Sulfur dioxide present in the atmosphere
reduces the amount of lichen covering the surrounding trees. Eventually,
industrial pollution came to the area, and sulfur
dioxide began
to kill the light-colored lichens off the trees, exposing the dark bark of the moths'
resting places, creating a drastic contrast in color and making the
light-colored moths more vulnerable to predation. This slowly altered the
balance of the population, as light-colored moths were not surviving to
reproduce and pass on their genes to the next generation, and the
darker-colored moths began to breed more due to their new-found rise in
fitness.[10] This reversal of survivability made the
gene contributing to melanic forms of the moth more desirable. The melanic
phenotype of the Biston
betularia has
been calculated to give a fitness advantage as great as 30 per cent.[11] As generations went on, eventually the
population of peppered moths transformed from the majority being light-colored
moths to the majority being dark-colored moths.
Melanic Biston
betularia have
also been widely observed in North America. In 1959, 90% of the Biston
betularia in Michigan
and Pennsylvania had the melanic phenotype.[12] By 2001, melanism dropped to 6% of the
population, following clean air legislation.[12] The drop in melanism is also correlated
with an increase in species richness of lichens, a decrease in atmospheric
sulfur dioxide, and an increase in the pale phenotype[13] The return of lichen and reduction of
atmospheric sulfur dioxide is directly correlated and helps illustrate how
influential air-pollution levels are to the frequency of melanism for Biston
betularia.
In each of these situations,
the melanized form of the organism was found in an environment in correlation
to higher amounts of industrial pollution found in the area. Many studies have
been done to determine the reasons for the favoritism of darker pigmentation.
Most studies aim to define the mechanism as a visual camouflage factor that
gives the darker-pigmented individuals a higher fitness, but some studies try
to find other ways that melanization can be an asset and, in turn, more
favorable than the lighter-pigmented individuals. It is thoroughly noted that
higher populations of darker-pigmented organisms develop when there is an
increase in industrial pollution in the area, but the relationship can not be
fully proven because the exact reason for increase in survivability can not be
tracked and pin-pointed.[14] To further solidify the theory of
industrial melanism as an actual selection factor within evolution, surveys of
melanic population rates and changes in atmospheric condition have been
reported to establish and confirm trends of favoritism of darker pigmented
individuals in an industrially polluted area. As government regulations of air
quality control have been implemented throughout the United States and the
United Kingdom, researchers have collected data on melanic populations before
and after the decontaminating effects of these regulations. According to their
results, melanic population rates are consistent with the theory of industrial
melanism, meaning that the level of melanic population was directly correlated
to the abundance of contaminated air quality. When the levels of atmospheric
pollution were high, so was the population rate of dark-colored moths, and when
the levels of atmospheric pollution were low, there was a decline of melanism
in the population.[14]
Industrial melanism is mostly
concerned with the visual effects of melanization. The idea is that the darker
pigmentation helps to camouflage the organisms better in an environment
darkened by pollution and therefore heightens the fitness by making it less
accessible to predators; but there are a few other ideas about why melanization
can help improve fitness in air-polluted areas for these populations that are
not correlated to any visual effect at all. It is theorized that organisms that
experience melanization have better immunity to toxic chemicals put into the
environment by industrial pollution. Other studies have been conceived to find
other aspects of melanization contributing to the survivability of the organism
other than visual inconspicuousness. In the black arches moth (Lymantria
monacha), it has been determined that the darker pigmented forms have
also developed a stronger immune response to foreign objects with the
attribution of the melanic pigment. The same melanic pigment that contributes
to the visual coloration of the moth is also involved in the encapsulation
process of foreign invaders through the immune defense of the dark-colored form
of the organism.[15] This enhanced defense against foreign
invaders is helpful in an environment contaminated by industrial pollution
because the toxins that are put out into the air have less chance of negatively
affecting the inhabitants of that environment.
Another proposed mechanism for
rapid industrial melanization is that there is a thermal advantage from the
darker coloration. Many suspect that this thermal advantage coupled with the
predation advantage, gives species such as the Biston betularia and Adalia bipunctata increased fitness.[16] The thermal advantage of industrial
melanism is directly linked to the pollution aspect of industrialization.[16] Smoke and particulates in the air reduce
the level of sunshine that reaches the habitats the Biston betularia and Adalia bipunctata. Melanic phenotypes become selectively
advantageous in this situation because the dark coloration allows for a more
efficient absorption of the limited sunlight.[9] In colder environments, the thermal
advantages of industrial melanism increases activity and the likelihood to
mate. In the Netherlands, melanic Adalia
bipunctata had a
distinct mating advantage over the non-melanic Adalia bipunctata[17] In the Adalia bipunctata, copulation is much more likely to occur
with warmer body temperatures and increased activity.[17] Increased body temperature also gives
melanic morphs a competitive advantage in searching for food because they are
more active.[9] Industrial melanism allows species such as
the Biston
betularia and the Adalia bipunctata to more efficiently warm their bodies in
environments of reduced sunshine, increasing their mating activity and
nutrition, thus increasing their fitness.
In felines[edit]
Melanistic coat coloration
occurs as a common polymorphism in 11
of 37 felid species and reaches high population
frequency in some cases but never achieves complete fixation. The black
panther, a melanic form of leopard, is
common in the equatorial rainforest of Malaya and the tropical rainforest on the
slopes of some African mountains, such as Mount
Kenya. The serval also has melanic forms in certain areas of East
Africa. In the jaguarundi,
coloration varies from dark brown and gray to light reddish. Melanic forms of jaguar are common in certain parts of South
America.[18] In 1938 and 1940, two melanistic bobcats were trapped alive in sub-tropical Florida.[19]
In 2003, the dominant mode of
inheritance of melanism in jaguars was confirmed by performing phenotype-transmission
analysis in a 116-individual captive pedigree. Melanistic animals were found to
carry at least one copy of a mutant MC1R sequence allele, bearing a 15-base pair inframe deletion. Ten
unrelated melanistic jaguars were either homozygous or heterozygous for this allele. A 24-base pair deletion
causes the incompletely dominant allele for melanism in the jaguarundi.
Sequencing of the agouti signalling peptide in the agouti
gene coding
region revealed a 2-base pair deletion in black domestic
cats. These variants were absent in melanistic individuals of Geoffroy’s cat, oncilla, pampas
cat and Asian
golden cat, suggesting that melanism arose independently at least four
times in the cat family.[20]
Melanism in leopards is
inherited as a Mendelian, monogenic recessive
trait relative
to the spotted form. Pairings of black animals have a significantly smaller
litter size than other possible pairings.[21] Between January 1996 and March 2009, leopards were photographed
at sixteen sites in the Malay
Peninsula in a
sampling effort of more than 1000 trap nights. Of 445 photographs of melanistic
leopards taken, 410 came from study sites south of the Kra
Isthmus, where the non-melanistic morph was never photographed. These
data suggest the near fixation of the dark allele in the region. The expected
time to fixation of this recessive allele due togenetic
drift alone
ranged from about 1,100 years to about 100,000 years.[22] Melanism in leopards has been hypothesized
to be causally associated with a selective advantage for ambush.[23]
In birds[edit]
In April 2015, an extremely
rare black flamingo was spotted on the Mediterranean island of Cyprus.[24]
Immune
system[edit]
Melanism related to the process
of adaptation is called adaptive. Most commonly, dark
individuals become fitter to survive and reproduce in their
environment as they are better camouflaged. This makes some species less
conspicuous to predators, while others, such as black
panthers, use it as a foraging advantage during night hunting.[6] Typically, adaptive melanism is heritable: A dominant gene, which
is entirely or nearly entirely expressed in the phenotype, is
responsible for the excessive amount of melanin.
Adaptive melanism has been
shown to occur in a variety of animals, including mammals such as squirrels, many felines andcanids, and coral
snakes. Adaptive melanism can lead to the creation of morphs, the most notable example being thepeppered
moth, whose evolutionary history in the United
Kingdom is
offered as a classic instructional tool for teaching the principles of natural
selection.[7]
Industrial Melanism[edit]
Industrial melanism is an
effect of urban pollution prominent in many species of arthropods. It is the
phenomenon of an organism evolving dark pigmentation when exposed to an
environment polluted by dark soot deposit and sulfuric buildup from industrial
pollution. In this type of industrial melanism, the darker pigmented
individuals develop a higher fitness and are favored by natural selection. This
change in favoritism as a result of modification in selection pressure is one
of the best-noted cases of Darwinian evolution.[8] The most common case of this adaptation is
found in the arthropod order Lepidoptera. This
order of insects encompasses all insects with microscopic scales on their
wings, such as moths and butterflies. Some species thought to undergo the
selection of industrial melanism are Adalia
bipunctata (two-spot
ladybird), Hamadryas
feronia(variable cracker butterfly), Odontopera bidentata (scalloped hazel moth), Oligia
latruncula (tawny
marbled minor moth),Oligia
strigilis (marbled
minor moth), and many other species of moths; but probably the best and most
studied example of industrial melanism is in the peppered moth, Biston
betularia. Originally, peppered moths lived where light-colored lichens
covered the trees where they would rest. To camouflage with the tree, they
originated with a light-colored pigment that helped them to avoid predators by
not being a visual distraction. Lichens are great bio-indicators of
air-pollution.[9] Sulfur dioxide present in the atmosphere
reduces the amount of lichen covering the surrounding trees. Eventually,
industrial pollution came to the area, and sulfur
dioxide began
to kill the light-colored lichens off the trees, exposing the dark bark of the
moths' resting places, creating a drastic contrast in color and making the
light-colored moths more vulnerable to predation. This slowly altered the
balance of the population, as light-colored moths were not surviving to
reproduce and pass on their genes to the next generation, and the
darker-colored moths began to breed more due to their new-found rise in
fitness.[10] This reversal of survivability made the
gene contributing to melanic forms of the moth more desirable. The melanic
phenotype of the Biston
betularia has
been calculated to give a fitness advantage as great as 30 per cent.[11] As generations went on, eventually the
population of peppered moths transformed from the majority being light-colored
moths to the majority being dark-colored moths.
Melanic Biston
betularia have
also been widely observed in North America. In 1959, 90% of the Biston
betularia in
Michigan and Pennsylvania had the melanic phenotype.[12] By 2001, melanism dropped to 6% of the
population, following clean air legislation.[12] The drop in melanism is also correlated
with an increase in species richness of lichens, a decrease in atmospheric
sulfur dioxide, and an increase in the pale phenotype[13] The return of lichen and reduction of
atmospheric sulfur dioxide is directly correlated and helps illustrate how
influential air-pollution levels are to the frequency of melanism for Biston
betularia.
In each of these situations,
the melanized form of the organism was found in an environment in correlation
to higher amounts of industrial pollution found in the area. Many studies have
been done to determine the reasons for the favoritism of darker pigmentation.
Most studies aim to define the mechanism as a visual camouflage factor that
gives the darker-pigmented individuals a higher fitness, but some studies try
to find other ways that melanization can be an asset and, in turn, more
favorable than the lighter-pigmented individuals. It is thoroughly noted that
higher populations of darker-pigmented organisms develop when there is an
increase in industrial pollution in the area, but the relationship can not be
fully proven because the exact reason for increase in survivability can not be
tracked and pin-pointed.[14] To further solidify the theory of
industrial melanism as an actual selection factor within evolution, surveys of
melanic population rates and changes in atmospheric condition have been
reported to establish and confirm trends of favoritism of darker pigmented
individuals in an industrially polluted area. As government regulations of air
quality control have been implemented throughout the United States and the
United Kingdom, researchers have collected data on melanic populations before
and after the decontaminating effects of these regulations. According to their
results, melanic population rates are consistent with the theory of industrial
melanism, meaning that the level of melanic population was directly correlated
to the abundance of contaminated air quality. When the levels of atmospheric
pollution were high, so was the population rate of dark-colored moths, and when
the levels of atmospheric pollution were low, there was a decline of melanism
in the population.[14]
Industrial melanism is mostly
concerned with the visual effects of melanization. The idea is that the darker
pigmentation helps to camouflage the organisms better in an environment
darkened by pollution and therefore heightens the fitness by making it less
accessible to predators; but there are a few other ideas about why melanization
can help improve fitness in air-polluted areas for these populations that are
not correlated to any visual effect at all. It is theorized that organisms that
experience melanization have better immunity to toxic chemicals put into the
environment by industrial pollution. Other studies have been conceived to find
other aspects of melanization contributing to the survivability of the organism
other than visual inconspicuousness. In the black arches moth (Lymantria
monacha), it has been determined that the darker pigmented forms have
also developed a stronger immune response to foreign objects with the
attribution of the melanic pigment. The same melanic pigment that contributes
to the visual coloration of the moth is also involved in the encapsulation
process of foreign invaders through the immune defense of the dark-colored form
of the organism.[15] This enhanced defense against foreign
invaders is helpful in an environment contaminated by industrial pollution
because the toxins that are put out into the air have less chance of negatively
affecting the inhabitants of that environment.
Another proposed mechanism for
rapid industrial melanization is that there is a thermal advantage from the
darker coloration. Many suspect that this thermal advantage coupled with the
predation advantage, gives species such as the Biston betularia and Adalia bipunctata increased fitness.[16] The thermal advantage of industrial
melanism is directly linked to the pollution aspect of industrialization.[16] Smoke and particulates in the air reduce
the level of sunshine that reaches the habitats the Biston betularia and Adalia bipunctata. Melanic phenotypes become selectively
advantageous in this situation because the dark coloration allows for a more
efficient absorption of the limited sunlight.[9] In colder environments, the thermal
advantages of industrial melanism increases activity and the likelihood to
mate. In the Netherlands, melanic Adalia
bipunctata had a
distinct mating advantage over the non-melanic Adalia bipunctata[17] In the Adalia bipunctata, copulation is much more likely to occur
with warmer body temperatures and increased activity.[17] Increased body temperature also gives
melanic morphs a competitive advantage in searching for food because they are
more active.[9] Industrial melanism allows species such as
the Biston
betularia and the Adalia bipunctata to more efficiently warm their bodies in
environments of reduced sunshine, increasing their mating activity and
nutrition, thus increasing their fitness.
In felines[edit]
Melanistic coat coloration
occurs as a common polymorphism in 11
of 37 felid species and reaches high population
frequency in some cases but never achieves complete fixation. The black
panther, a melanic form of leopard, is
common in the equatorial rainforest of Malaya and the tropical rainforest on the
slopes of some African mountains, such as Mount
Kenya. The serval also has melanic forms in certain areas of East
Africa. In the jaguarundi,
coloration varies from dark brown and gray to light reddish. Melanic forms of jaguar are common in certain parts of South
America.[18] In 1938 and 1940, two melanistic bobcats were trapped alive in sub-tropical Florida.[19]
In 2003, the dominant mode of
inheritance of melanism in jaguars was confirmed by performing phenotype-transmission
analysis in a 116-individual captive pedigree.
Melanistic animals were found to carry at least one copy of a mutant MC1R sequence allele,
bearing a 15-base pair inframe
deletion. Ten unrelated melanistic jaguars were either homozygous or heterozygous for this allele. A 24-base pair deletion
causes the incompletely dominant allele for melanism in the jaguarundi.
Sequencing of the agouti signalling peptide in the agouti
gene coding
region revealed a 2-base pair deletion in black domestic
cats. These variants were absent in melanistic individuals of Geoffroy’s cat, oncilla, pampas
cat and Asian
golden cat, suggesting that melanism arose independently at least four
times in the cat family.[20]
Melanism in leopards is
inherited as a Mendelian, monogenic recessive
trait relative
to the spotted form. Pairings of black animals have a significantly smaller
litter size than other possible pairings.[21] Between January 1996 and March 2009, leopards were
photographed at sixteen sites in the Malay Peninsula in a sampling effort of more than 1000 trap
nights. Of 445 photographs of melanistic leopards taken, 410 came from study
sites south of the Kra
Isthmus, where the non-melanistic morph was never photographed. These
data suggest the near fixation of the dark allele in the region. The expected
time to fixation of this recessive allele due togenetic
drift alone
ranged from about 1,100 years to about 100,000 years.[22] Melanism in leopards has been hypothesized
to be causally associated with a selective advantage for ambush.[23]
In birds[edit]
In April 2015, an extremely
rare black flamingo was spotted on the Mediterranean island of Cyprus.[24]
Immune
system[edit]
Melanin has several
physiological roles in maintaining health, such as the synthesis of vitamin D.
Melanin is the primary determinant of the degree of skin pigmentation and protects
the body from harmful ultraviolet radiation. Synthesis of 1,25-dihydroxyvitamin
D3 in the
skin, however, is dependent on ultraviolet
B light.
Highly pigmented skin, to the level found in people of African origin, abrogates almost all
ultraviolet-induced 1,25-(OH)2D3 synthesis. Numerous animal models and
clinical studies have underlined the essential role of vitamin D as a modulator
of the different processes of the immune
system. Evidence indicates that serum concentrations of 1,25-(OH)2D3 and the prevalence of autoimmune diseases in a
certain population are associated with the latitude at which that population
resides.[25]
Genes for melanism in felines
may provide resistance to viral infections. A viral epidemic may explain the
prevalence of black leopards in Java and Malaysia and the relatively high incidence of black leopards and black servals in the Aberdares region of Africa. Previously, black-furred
felines in the Aberdares had been considered a high-altitude adaptation, since
black fur absorbs more heat.[26]
Studies reported in New
Scientist magazine
in 2003 also suggested that recessive-gene melanism is linked to disease
resistance rather than altitude. Melanistic cats may have better resistance to
disease than cats with "normal" color coats. This would explain why
recessive melanism persists when melanistic individuals are disadvantaged
because they are poorly camouflaged in open areas.
Socio-politics[edit]
The term melanism has been used on Usenet, internet
forums and blogs to mean
an African-American social
movement holding
that dark-skinned humans are the original people from which those of other skin
colour originate.
The term melanism has been used in this context as early as
the mid-1990s[27] and was promoted by some Afrocentrists, such
as Frances Cress Welsing.
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This page was last modified on 1 October 2016, at 11:35.
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10
Incredible Melanistic (All Black) Animals
Melanism is an undue development
of dark-colored pigment in the skin or its appendages and is the opposite of
albinism. The word ‘melanism’ is deduced from a Greek word that means black
pigment. Pseudo-melanism, also called abundism, is another variant of
pigmentation, characterized by dark spots or enlarged stripes, which cover a
large part of the body of the animal making it appear melanistic.
Melanism related to the process
of adaptation is called adaptive.
Most commonly, dark individuals become fitter to survive and reproduce in their
environment as they are better camouflaged. This makes some species less
conspicuous to predators, while others such as black panthers use it as a
foraging advantage during night hunting. Typically adaptive melanism is
heritable: A dominant gene, which is entirely or nearly entirely expressed in
the phenotype is responsible for the excessive amount of melanin. Adaptive
melanism has been shown to occur in a variety of animals, including mammals
such as squirrels, many felines and canids, and coral snakes. [Source: Wikipedia]
Below
you will find a fascinating gallery of ten melanistic (all black) animals. If
you know of other melanistic animals, please post in the comments below!
...............................
Industrial melanism
industrial melanism, the darkness—of the skin, feathers, or
fur—acquired by a population of animals living in an industrial region where
the environment is soot-darkened. The melanization of a
population increases the probability that its members will survive and
reproduce; it takes place over the course of many generations as the result of natural selection of the lighter, more conspicuous
animals by predators.
............................
Review
Heredity (2013) 110, 207–212; doi:10.1038/hdy.2012.92; published online 5 December 2012
The peppered
moth and industrial
melanism: evolution of a natural selection case study
1. 1Faculty
of Life Sciences, School of Life Sciences, University of Manchester,
Manchester, UK
2. 2Institute
of Integrative Biology, University of Liverpool, Liverpool, UK
Correspondence: Dr LM Cook, Faculty of Life
Sciences, School of Life Sciences, University of Manchester, Oxford Road,
Manchester M13 9PT, UK. E-mail: lcook@manchester.ac.uk
Received
9 August 2012; Revised 1 October 2012; Accepted
15 October 2012
Advance online publication 5 December 2012
Advance online publication 5 December 2012
Abstract
From the outset multiple causes have been suggested for changes in
melanic gene frequency in the peppered moth Biston betularia and other industrial melanic moths.
These have included higher intrinsic fitness of melanic forms and selective
predation for camouflage. The possible existence and origin of
heterozygote advantage has been debated. From the 1950s, as a result of
experimental evidence, selective predation became the favoured explanation and
is undoubtedly the major factor driving the frequency change. However,
modelling and monitoring of declining melanic frequencies since the 1970s
indicate either that migration rates are much higher than existing direct
estimates suggested or else, or in addition, non-visual selection has a role.
Recent molecular work on genetics has revealed that the melanic (carbonaria)
allele had a single origin in Britain, and that the locus is orthologous to a
major wing patterning locus in Heliconius butterflies. New methods of analysis should supply further information
on the melanic system and on migration that will complete our understanding of
this important example of rapid evolution. http://www.nature.com/hdy/journal/v97/n3/full/6800861a.html
Keywords:
Biston betularia; carbonaria gene; mutation; predation; non-visual selection;
migration
.....................
Industrial Melanism in Action
Normally, evolutionary
pressures change only slowly, meaning that genetic change and natural selection
moves very slowly. This began to change with the increasing industrialization
of human societies.
The Industrial Revolution, in
Britain, burned vast amounts of coal, producing sulfur dioxide that killed off
all the lichens. Factories also threw out huge amounts of black soot, covering
every building and every tree with black grime.
All of a sudden, evolutionary pressure on the peppered moth
began to change. Light colored moths resting on a tree now stood out against
the black background and were more likely to be eaten. The darker variant, on the other hand, was now
camouflaged, and more likely to survive and breed. In a textbook case of industrial melanism , in just a few generations, the dark
variant became by far the most common.
In just over 50 years, the dark variety went from making up just 2% of
the population to making up over 95%, a change that could not be explained by
any theory other than natural selection and industrial melanism.
Genetic drift, where random
influences can change the genetic make up of a population over time, is far too
slow a process to account for this.
In genetic terms, the gene for
dark color, as in most species, is dominant; once the pressure of predation was
removed, this variant quickly spread. This is borne out by the fact that the
American variant of the species changed in exactly the same way, a process
known as convergent evolution.
Re-Adaptation
Strangely enough, now that
modern industry in Europe is using cleaner technologies, the moth is now
returning back to the typical variety, as the selection pressure from predation
has now reversed.
Because the allele for the
lighter color is recessive and requires a copy from both parents, it is a
slower process than the initial change. This is known as reverse industrial
melanism.
Micro-Evolution
The incidence of industrial melanism is a process called
micro-evolution, where selection pressures within a species lead to changes.
In time, when mixed with
genetic drift, other mutations and other possible selection pressures, this
process of micro-evolution could have led to specialization within the peppered
moth population.
If you have two separate populations living in sooty areas and
natural areas, with little mixing between the two, random fluctuations could
well lead to them becoming distinct species, as withDarwin’s finches.
.......................
Industrial Melanism (Insects)
Industrial melanism may be defined as a proportional
increase of dark, or melanin, pigments in individuals of a population, caused
by changes in the environment resulting from industrial pollution. Both increases in the
frequencies of distinct melanic forms and the general darkening of some or all
forms within a population may be involved.
The increase in dark forms of some species of moth in industrial regions of Western Europe, and latterly elsewhere, has provided some of the best known, most easily understood, and most often quoted examples of evolution in action. Increases in pollution following the industrial revolution led to changes in the environment. In particular, sulfur dioxide denuded trees and other substrates of lichens, while particulate air pollution blackened the resulting surfaces. In response to these changes, the color patterns of many species of moth and some other invertebrates that rely on camouflage for defense against some predators have changed, becoming darker, in line with the darkening of the substrates that they rest upon by day. These changes have occurred largely in the past 150 years and are cited as examples that illustrate the central mechanism of Charles Darwin’s theory of evolution: natural selection.
The increase in dark forms of some species of moth in industrial regions of Western Europe, and latterly elsewhere, has provided some of the best known, most easily understood, and most often quoted examples of evolution in action. Increases in pollution following the industrial revolution led to changes in the environment. In particular, sulfur dioxide denuded trees and other substrates of lichens, while particulate air pollution blackened the resulting surfaces. In response to these changes, the color patterns of many species of moth and some other invertebrates that rely on camouflage for defense against some predators have changed, becoming darker, in line with the darkening of the substrates that they rest upon by day. These changes have occurred largely in the past 150 years and are cited as examples that illustrate the central mechanism of Charles Darwin’s theory of evolution: natural selection.
TYPES OF INDUSTRIAL MELANISM
Three categories of industrial
melanism have been recognized:
A. Full industrial melanic polymorphism involves distinct
melanic forms that have arisen since the industrial revolution and have
increased as a consequence of the effects of industrialization on the
environment.
B. Partial industrial melanic polymorphism involves polymorphic species that had distinct melanic forms prior to the industrial revolution.
These forms have increased in frequency following and as a consequence of the effects of industrialization.
B. Partial industrial melanic polymorphism involves polymorphic species that had distinct melanic forms prior to the industrial revolution.
These forms have increased in frequency following and as a consequence of the effects of industrialization.
C. Polygenic industrial melanism involves species in
which the average ground color of some or all members of a population has
darkened gradually as a consequence of the effects of industrialization.
It should be noted that melanism is a common phenomenon throughout the animal kingdom, with many factors unrelated to industrialization or pollution influencing the success of melanic forms in some species, including humans.
It should be noted that melanism is a common phenomenon throughout the animal kingdom, with many factors unrelated to industrialization or pollution influencing the success of melanic forms in some species, including humans.
FULL INDUSTRIAL MELANIC POLYMORPHISM
The Peppered Moth
The peppered moth,
Biston betularia, has dominated the literature on industrial melanism. In
Britain, the ancestral form of this species (form t ypica) is white, liberally
speckled with dark brown or black scales (Fig. 1). In 1848, a predominantly
black form of B. betularia, form carbonaria (Fig. 2) , was recorded in
Manchester, England. Within 50 years, 98% of Mancunian peppered moths were
black. From this original location, carbonaria spread to many other parts of
Britain. In 1896, the renowned Victorian lepidopterist J. W
FIGURE 1 The typical form of the peppered moth, B. betularia.
FIGURE 2 The carbonaria form of the peppered moth.
Tutt suggested that camouflage and bird predation could be involved in the spread of carbonaria. Arguing that the typical form was camouflaged well on surfaces covered by lichens, he noted that many natural surfaces had changed as a consequence of pollutants resulting from heavy industry. In particular, the combined effects of sulfur dioxide, which killed foliose lichens, and soot fallout, which blackened the denuded surfaces, had led to darker and more uniform substrates. He stated that on these surfaces carbonaria would be better camouflaged than typica and so gain protection from bird predation. Natural selection, through the medium of differential bird preda-tion, augmented by “hereditary tendency,” had led to an increase in the frequency of the black form.
Tutt’s hypothesis was largely rejected for over 50 years because most entomologists and ornithologists concurred in the view that birds are not major predators of cryptic, day-resting moths. A variety of other explanations for the increase in melanic forms of some moths were thus put forward during this period (pollutants acting as mutagenic agents, Lamarckian evolution, and heterozygote advantage).
One important advance during this period was the calculation by Haldane in 1924 that carbonaria would have to have been 1.5 times as fit as typica to account for the rapidity of the rise in carbonaria frequency in Manchester. This fitness difference was much higher than most evolutionary biologists of the time thought feasible.
In the 1950s, Tutt’s bird predation explanation of industrial melanism was tested by scientific experimentation. Dr. Bernard Kettlewell, using direct observation of the predation of live moths released onto tree trunks, and mark-release-recapture techniques, in two populations, one in a polluted and the other in a nonpolluted oak woodland, obtained strong evidence to support Tutt’s differential predation hypothesis. Both experiments showed that the typica form of the moth had lower fitness than carbonaria in the polluted woodland but a higher fitness in the nonpolluted wood. It was the fact that Kettlewell obtained reciprocal results in the two environments that made his conclusions convincing. Kettlewell also mapped the frequency of carbonaria against sulfur dioxide and soot fallout, finding a significant correlation between the frequency of carbonaria and both pollutants, that with sulfur dioxide being strongest.
Kettlewell’s work made the case of industrial melanism in the peppered moth the most cited example of evolution in action through an identified agent of natural selection: differential bird predation. As Professor Sewall Wright wrote in 1978, industrial melanism in the peppered moth provided “the clearest case in which a conspicuous evolutionary process has actually been witnessed.” Here was Darwin’s missing evidence.
Since the 1960s, many other studies have been carried out on the peppered moth. Some have focused on the fine details of the case, including the intermediate form insularia ( Fig. 3 ). Others have considered how the peppered moth has been affected by antipollution legislation, while still others have addressed criticisms of some of Kettlewell’s experimental protocols.
FIGURE 1 The typical form of the peppered moth, B. betularia.
FIGURE 2 The carbonaria form of the peppered moth.
Tutt suggested that camouflage and bird predation could be involved in the spread of carbonaria. Arguing that the typical form was camouflaged well on surfaces covered by lichens, he noted that many natural surfaces had changed as a consequence of pollutants resulting from heavy industry. In particular, the combined effects of sulfur dioxide, which killed foliose lichens, and soot fallout, which blackened the denuded surfaces, had led to darker and more uniform substrates. He stated that on these surfaces carbonaria would be better camouflaged than typica and so gain protection from bird predation. Natural selection, through the medium of differential bird preda-tion, augmented by “hereditary tendency,” had led to an increase in the frequency of the black form.
Tutt’s hypothesis was largely rejected for over 50 years because most entomologists and ornithologists concurred in the view that birds are not major predators of cryptic, day-resting moths. A variety of other explanations for the increase in melanic forms of some moths were thus put forward during this period (pollutants acting as mutagenic agents, Lamarckian evolution, and heterozygote advantage).
One important advance during this period was the calculation by Haldane in 1924 that carbonaria would have to have been 1.5 times as fit as typica to account for the rapidity of the rise in carbonaria frequency in Manchester. This fitness difference was much higher than most evolutionary biologists of the time thought feasible.
In the 1950s, Tutt’s bird predation explanation of industrial melanism was tested by scientific experimentation. Dr. Bernard Kettlewell, using direct observation of the predation of live moths released onto tree trunks, and mark-release-recapture techniques, in two populations, one in a polluted and the other in a nonpolluted oak woodland, obtained strong evidence to support Tutt’s differential predation hypothesis. Both experiments showed that the typica form of the moth had lower fitness than carbonaria in the polluted woodland but a higher fitness in the nonpolluted wood. It was the fact that Kettlewell obtained reciprocal results in the two environments that made his conclusions convincing. Kettlewell also mapped the frequency of carbonaria against sulfur dioxide and soot fallout, finding a significant correlation between the frequency of carbonaria and both pollutants, that with sulfur dioxide being strongest.
Kettlewell’s work made the case of industrial melanism in the peppered moth the most cited example of evolution in action through an identified agent of natural selection: differential bird predation. As Professor Sewall Wright wrote in 1978, industrial melanism in the peppered moth provided “the clearest case in which a conspicuous evolutionary process has actually been witnessed.” Here was Darwin’s missing evidence.
Since the 1960s, many other studies have been carried out on the peppered moth. Some have focused on the fine details of the case, including the intermediate form insularia ( Fig. 3 ). Others have considered how the peppered moth has been affected by antipollution legislation, while still others have addressed criticisms of some of Kettlewell’s experimental protocols.
The main elements of the peppered moth case as they are now known are:
1. The melanic,
carbonaria form of the peppered moth was first recorded in 1848.
2. This carbonaria form is controlled by a mutant allele of a single gene, which is genetically dominant to the allele controlling the pale typica form.
3. The carbonaria form spread and increased rapidly in industrial regions of Britain but not in rural regions.
FIGURE 3 The peppered moth has a third intermediate form, insularia.
4. Peppered moths rest by day on the bark of trees.
5. Birds find peppered moths on tree bark and eat them.
6. The likelihood of a moth being found by a bird depends on its degree of camouflage.
7. Nonmelanic peppered moths are better camouflaged than mela-nics on lichen-covered tree bark. Melanic peppered moths are better camouflaged than nonmelanics in areas where tree bark has been denuded of lichens and blackened by soot fallout.
8. The frequencies of melanic and nonmelanic moths in a particular area depend on the level of bird predation of each form and the rate of migration of moths into the area from adjacent districts in which the form frequencies are different.
9. Following the Clean Air Acts and other antipollution legislation of the 1950s and subsequently, levels of pollution in Britain have declined, bark is no longer heavily soot covered, and lichens have regrown to a significant extent. Since the mid-1960s, the frequencies of carbonaria have declined substantially in Britain.
10. Rates of decline are broadly in line with theoretical predictions from computer simulations. If the decline in carbonaria continues at its present rate, this form will be reduced in Britain to the status of a rare mutation by 2020.
11. Similar declines in melanic frequencies correlated to declines in pollution levels have been observed in Holland and in the United States.
Data on the declines of the melanic forms of the peppered moth in Britain, continental Europe, and America are important for three reasons. First, they show that evolution is not a one-way process. Evolutionary changes can be reversed if the selective factors that lead to them are reversed. Second, the data sets from different populations in Europe and America , in effect, replicate natural experiments. The consistency in the patterns of increase and decrease in the frequencies of melanic forms correlated to pollution
FIGURE 4 A peppered moth in its most common resting position, on a lateral tree branch.
levels adds weight to the selective explanation of the evolutionary changes observed. Third, the accord between predicted decreases in melanic frequencies and the observed frequencies currently being recorded argues that the factors incorporated into the models are broadly correct.
Since 1998, the case of the peppered moth has been attacked by antievolution lobbyists, who have emphasized both weaknesses in Kettlewell’s experimental procedures and differences in opinions between scientists who have worked on or commented on the case. The case has thus been at the center of the evolution vs. creation debate, with calls being made, particularly in the United States, for it to be removed from biology text topics. It is notable that the focus of these criticisms is almost invariably the well-known experiments of Kettlewell, whereas later independent experiments in which improved protocols have been used, and which have led to the same basic deductions as Kettlewell’s work, are not cited. The controversy took another turn in 2002, when a journalist, Judith Hooper, published a topic in which she makes thinly veiled accusations of data fudging and scientific fraud aimed at Kettlewell, and a conspiracy of silence aimed at the scientists who have conducted the experimental work on the peppered moth.
The controversy over the peppered moth case has engendered new interest in the case, with scientific historians examining the accusations of fraud aimed at Kettlewell. The conclusion of these examinations is that there is not one shred of evidence to support Hooper’s accusations. In addition, a new series of experiments have been undertaken to address the flaws in Kettlewell’s experiments and address other issues raised by the antievolution lobby. In brief, these have shown that (1) the peppered moths do rest by day on the bark of deciduous trees, most commonly on the underside of lateral branches (Fig. 4) but also sometimes on the trunks; (2) that bats feeding on peppered moths at night do not differentiate between the forms of the peppered moth, refuting the suggestion that they, rather than birds, could be the agent of selection; (3) that greater levels of bird predation of carbonaria, compared with typica, in a 6-year period from 2002 to 2007, is entirely sufficient to explain the observed decline in carbonaria frequency in Cambridge, England, over this period. This work fully supports Tutt’s differential bird predation hypothesis.
FIGURE 5 Nonmelanic and melanic forms of the brindled beauty, L. hirtaria.
2. This carbonaria form is controlled by a mutant allele of a single gene, which is genetically dominant to the allele controlling the pale typica form.
3. The carbonaria form spread and increased rapidly in industrial regions of Britain but not in rural regions.
FIGURE 3 The peppered moth has a third intermediate form, insularia.
4. Peppered moths rest by day on the bark of trees.
5. Birds find peppered moths on tree bark and eat them.
6. The likelihood of a moth being found by a bird depends on its degree of camouflage.
7. Nonmelanic peppered moths are better camouflaged than mela-nics on lichen-covered tree bark. Melanic peppered moths are better camouflaged than nonmelanics in areas where tree bark has been denuded of lichens and blackened by soot fallout.
8. The frequencies of melanic and nonmelanic moths in a particular area depend on the level of bird predation of each form and the rate of migration of moths into the area from adjacent districts in which the form frequencies are different.
9. Following the Clean Air Acts and other antipollution legislation of the 1950s and subsequently, levels of pollution in Britain have declined, bark is no longer heavily soot covered, and lichens have regrown to a significant extent. Since the mid-1960s, the frequencies of carbonaria have declined substantially in Britain.
10. Rates of decline are broadly in line with theoretical predictions from computer simulations. If the decline in carbonaria continues at its present rate, this form will be reduced in Britain to the status of a rare mutation by 2020.
11. Similar declines in melanic frequencies correlated to declines in pollution levels have been observed in Holland and in the United States.
Data on the declines of the melanic forms of the peppered moth in Britain, continental Europe, and America are important for three reasons. First, they show that evolution is not a one-way process. Evolutionary changes can be reversed if the selective factors that lead to them are reversed. Second, the data sets from different populations in Europe and America , in effect, replicate natural experiments. The consistency in the patterns of increase and decrease in the frequencies of melanic forms correlated to pollution
FIGURE 4 A peppered moth in its most common resting position, on a lateral tree branch.
levels adds weight to the selective explanation of the evolutionary changes observed. Third, the accord between predicted decreases in melanic frequencies and the observed frequencies currently being recorded argues that the factors incorporated into the models are broadly correct.
Since 1998, the case of the peppered moth has been attacked by antievolution lobbyists, who have emphasized both weaknesses in Kettlewell’s experimental procedures and differences in opinions between scientists who have worked on or commented on the case. The case has thus been at the center of the evolution vs. creation debate, with calls being made, particularly in the United States, for it to be removed from biology text topics. It is notable that the focus of these criticisms is almost invariably the well-known experiments of Kettlewell, whereas later independent experiments in which improved protocols have been used, and which have led to the same basic deductions as Kettlewell’s work, are not cited. The controversy took another turn in 2002, when a journalist, Judith Hooper, published a topic in which she makes thinly veiled accusations of data fudging and scientific fraud aimed at Kettlewell, and a conspiracy of silence aimed at the scientists who have conducted the experimental work on the peppered moth.
The controversy over the peppered moth case has engendered new interest in the case, with scientific historians examining the accusations of fraud aimed at Kettlewell. The conclusion of these examinations is that there is not one shred of evidence to support Hooper’s accusations. In addition, a new series of experiments have been undertaken to address the flaws in Kettlewell’s experiments and address other issues raised by the antievolution lobby. In brief, these have shown that (1) the peppered moths do rest by day on the bark of deciduous trees, most commonly on the underside of lateral branches (Fig. 4) but also sometimes on the trunks; (2) that bats feeding on peppered moths at night do not differentiate between the forms of the peppered moth, refuting the suggestion that they, rather than birds, could be the agent of selection; (3) that greater levels of bird predation of carbonaria, compared with typica, in a 6-year period from 2002 to 2007, is entirely sufficient to explain the observed decline in carbonaria frequency in Cambridge, England, over this period. This work fully supports Tutt’s differential bird predation hypothesis.
FIGURE 5 Nonmelanic and melanic forms of the brindled beauty, L. hirtaria.
Other Examples of Full Industrial Melanic Polymorphism
The vast majority of
research and comment on industrial melanism has been focused on the peppered
moth. However, the case of the peppered moth is not unique. A small number of
other examples of full industrial melanic polymorphism are known. The mela-nic
forms in most of these cases are controlled by dominant alleles of single
genes. An exception is that of the brindled beauty, Lycia hirtaria, in which
the melanic form nigra ( Fig. 5 ) is controlled by a recessive allele. That
most recent melanic forms are genetically dominant is not surprising because a
dominant mutation will be fully expressed as soon as it arises and will quickly
be favored by selection if advantageous. Recessive mutations would not be
exposed to selection until they occurred in homozygotes in which their effects
would be expressed phenotypically.
In some species showing full industrial melanic polymorphism, such as the lobster moth, Stauropus fagi, melanism developed at roughly the same time as in the peppered moth. In others, industrial melanism has developed much more recently, as in the cases of the sprawler, Brachionycha sphinx, and the early grey, Xylocampa areola, in which industrial melanism developed only in the second half of the 20th century. The reason that industrial melanism did not evolve earlier in these species is probably serendipitous: a melanic mutation simply did not occur previously in an appropriate population.
The different timings of the initial occurrence of industrial mela-nics of different species help emphasize that natural selection cannot cause change unless phenotypic variation exists. This is manifest in the oak beauty moth, Biston strataria. the closest British relative of the peppered moth. The oak beauty has a melanic form, melanaria, which is a common industrial melanic in Holland, but has never been recorded, except as a rare mutation, in Britain. In terms of its ecology, behavior, and distribution, the oak beauty is similar to the peppered moth. However, the melanaria mutation seems never to have arisen in Britain in favorable circumstances nor has this form reached Britain from continental Europe as a migrant. Melanism in the oak beauty in Europe can be contrasted with that of another moth, the figure of eighty, Tethea ocularis. The melanic form, fusca, of this species was known in Belgium and Holland in the early part of the 20th century but was absent from Britain. This form arrived in southern England, by migration, in the mid-1940s. Following its arrival, f. fusca spread to many industrial parts of Britain and increased in frequency rapidly, although its frequency is now declining again in response to reductions in pollution.
The current declines in melanism seen in the peppered moth, the figure of eighty, and several other species, following antipollution legislation, suggest that future studies of industrial melanism may have to shift to countries in which industrialization is still increasing and antipollution measures are as yet limited.
In some species showing full industrial melanic polymorphism, such as the lobster moth, Stauropus fagi, melanism developed at roughly the same time as in the peppered moth. In others, industrial melanism has developed much more recently, as in the cases of the sprawler, Brachionycha sphinx, and the early grey, Xylocampa areola, in which industrial melanism developed only in the second half of the 20th century. The reason that industrial melanism did not evolve earlier in these species is probably serendipitous: a melanic mutation simply did not occur previously in an appropriate population.
The different timings of the initial occurrence of industrial mela-nics of different species help emphasize that natural selection cannot cause change unless phenotypic variation exists. This is manifest in the oak beauty moth, Biston strataria. the closest British relative of the peppered moth. The oak beauty has a melanic form, melanaria, which is a common industrial melanic in Holland, but has never been recorded, except as a rare mutation, in Britain. In terms of its ecology, behavior, and distribution, the oak beauty is similar to the peppered moth. However, the melanaria mutation seems never to have arisen in Britain in favorable circumstances nor has this form reached Britain from continental Europe as a migrant. Melanism in the oak beauty in Europe can be contrasted with that of another moth, the figure of eighty, Tethea ocularis. The melanic form, fusca, of this species was known in Belgium and Holland in the early part of the 20th century but was absent from Britain. This form arrived in southern England, by migration, in the mid-1940s. Following its arrival, f. fusca spread to many industrial parts of Britain and increased in frequency rapidly, although its frequency is now declining again in response to reductions in pollution.
The current declines in melanism seen in the peppered moth, the figure of eighty, and several other species, following antipollution legislation, suggest that future studies of industrial melanism may have to shift to countries in which industrialization is still increasing and antipollution measures are as yet limited.
PARTIAL INDUSTRIAL MELANIC POLYMORPHISM
Melanic forms of many
species of moth are independent of industrialization. The factors that can
favor melanism are numerous and varied. These have been discussed in detail by
Kettlewell and Majerus. Their relevance to industrial melanism is that in some
moths, the presence of melanic forms prior to, and independent of,
industrialization provided a repository of melanic variants that were favored
as pollution levels increased.
Indeed, it is likely that the majority of moths that exhibit melanic polymorphism, with melanic frequency correlated to pollution levels, had melanic forms occurring at relatively low equilibrium frequencies prior to the industrial revolution. Changes in the environment resulting from increased pollution favored these dark forms and their frequencies increased. The willow beauty, Peribatodes rhomboidaria, well illustrates this idea. In Britain, this species has long had a non-industrial melanic form, perfumaria. The perfumaria form greatly increased in frequency in industrial regions in the late 19th century. In the 20th century, perfumaria, which still occurs at low frequency in some rural areas, particularly in Scotland, was replaced in industrial areas, but not elsewhere, by an even darker form, f. rebeli. Here then, f. perfumaria should be regarded as a partial industrial mela-nic, while f. rebeli is a full industrial melanic.
Many probable instances of partial industrial melanic polymorphism could be cited, but rather few of the species that fall into this class of melanism have been investigated in depth. Exceptions are the pale brindled beauty, Phigalia pilosaria (Fig. 6A and 6B); the mottled beauty, Alcis repandata; and the green brindled crescent, Allophyes oxyacanthae. All are bark-resters, the increase in melanics in industrial regions being attributed to increased crypsis.
Some of these species show morph-specific habitat preferences. Morph-specific habitat preferences in Lepidoptera showing melanic polymorphism were first suggested to explain abrupt differences in melanic frequencies of the mottled beauty and the tawny-barred angle, Semiothisa liturata, either side of sharp habitat boundaries. Such differences have subsequently been recorded in 14 species, in all cases melanics having higher frequencies in woodland with dense canopies than in adjacent more open habitats.
Many species that now have industrial melanics first evolved melanism in specific ecological circumstances prior to industrialization. It is known, for example, that a number of species now show mela-nic polymorphism in unpolluted ancient coniferous forests, such as Rannoch Black Wood in Scotland. Similar habitats were more widespread in the past and are likely to have supported melanic forms. These melanic forms would have been at a selective disadvantage if they moved from areas with the specific ecological circumstances to which they were adapted. Consequently, the melanics evolved behaviors that restricted them to such habitats. Recent changes in forestry and land usage and increases in pollution have provided new habitats (e.g., conifer plantations and polluted woodlands) with ecological conditions that favor melanics. The melanics have consequently spread
FIGURE 6 Nonmelanic (A) and melanic (B) forms of the pale brindled beauty, P. pilosaria.
and risen in frequency, producing examples of partial industrial mel-anic polymorphism in which morph-specific habitat preferences are retained to some extent.
Indeed, it is likely that the majority of moths that exhibit melanic polymorphism, with melanic frequency correlated to pollution levels, had melanic forms occurring at relatively low equilibrium frequencies prior to the industrial revolution. Changes in the environment resulting from increased pollution favored these dark forms and their frequencies increased. The willow beauty, Peribatodes rhomboidaria, well illustrates this idea. In Britain, this species has long had a non-industrial melanic form, perfumaria. The perfumaria form greatly increased in frequency in industrial regions in the late 19th century. In the 20th century, perfumaria, which still occurs at low frequency in some rural areas, particularly in Scotland, was replaced in industrial areas, but not elsewhere, by an even darker form, f. rebeli. Here then, f. perfumaria should be regarded as a partial industrial mela-nic, while f. rebeli is a full industrial melanic.
Many probable instances of partial industrial melanic polymorphism could be cited, but rather few of the species that fall into this class of melanism have been investigated in depth. Exceptions are the pale brindled beauty, Phigalia pilosaria (Fig. 6A and 6B); the mottled beauty, Alcis repandata; and the green brindled crescent, Allophyes oxyacanthae. All are bark-resters, the increase in melanics in industrial regions being attributed to increased crypsis.
Some of these species show morph-specific habitat preferences. Morph-specific habitat preferences in Lepidoptera showing melanic polymorphism were first suggested to explain abrupt differences in melanic frequencies of the mottled beauty and the tawny-barred angle, Semiothisa liturata, either side of sharp habitat boundaries. Such differences have subsequently been recorded in 14 species, in all cases melanics having higher frequencies in woodland with dense canopies than in adjacent more open habitats.
Many species that now have industrial melanics first evolved melanism in specific ecological circumstances prior to industrialization. It is known, for example, that a number of species now show mela-nic polymorphism in unpolluted ancient coniferous forests, such as Rannoch Black Wood in Scotland. Similar habitats were more widespread in the past and are likely to have supported melanic forms. These melanic forms would have been at a selective disadvantage if they moved from areas with the specific ecological circumstances to which they were adapted. Consequently, the melanics evolved behaviors that restricted them to such habitats. Recent changes in forestry and land usage and increases in pollution have provided new habitats (e.g., conifer plantations and polluted woodlands) with ecological conditions that favor melanics. The melanics have consequently spread
FIGURE 6 Nonmelanic (A) and melanic (B) forms of the pale brindled beauty, P. pilosaria.
and risen in frequency, producing examples of partial industrial mel-anic polymorphism in which morph-specific habitat preferences are retained to some extent.
POLYGENIC INDUSTRIAL MELANISM
Of all categories of
melanism, polygenic industrial melanism has been the least considered and is
the most difficult to address. Examination of specimens collected over the past
century and a half suggests that many species have experienced a gradual
darkening of the colors and loss of patterning in industrial regions,
irrespective of morph. Although some of this change may be attributed to the
gradual fading that occurs in museum specimens with time, it is difficult to
ascribe all of the differences to this phenomenon. Comparison of series of
specimens of six species, from rural and industrial regions, collected between
1880 and 1914 with those collected between 1992 and 1996 showed that the ground
color had darkened more in industrial regions than in the rural areas.
This gradual darkening is probably the result of selection acting on polygenic variation. Small variations in the color patterns of many species are known to be controlled by many genes, each having a small effect. The selective predation of lighter and thus less cryptic forms in regions affected by particulate air pollution will result in those alleles which produce darker morphs increasing in frequency. It is difficult to see how this hypothesis can be tested. However, if it is correct, the recent decrease in pollution should lead to a reversal of this trend, with ground colors lightening and patterns becoming more clearly defined again. Novel, digital methods of measuring the spectral reflectance of surfaces and storing data should allow measurement without reliance on museum specimens or photographs, both of which may fade with time.
This gradual darkening is probably the result of selection acting on polygenic variation. Small variations in the color patterns of many species are known to be controlled by many genes, each having a small effect. The selective predation of lighter and thus less cryptic forms in regions affected by particulate air pollution will result in those alleles which produce darker morphs increasing in frequency. It is difficult to see how this hypothesis can be tested. However, if it is correct, the recent decrease in pollution should lead to a reversal of this trend, with ground colors lightening and patterns becoming more clearly defined again. Novel, digital methods of measuring the spectral reflectance of surfaces and storing data should allow measurement without reliance on museum specimens or photographs, both of which may fade with time.
MELANISM AND THE STUDY OF EVOLUTION
The significance of
industrial melanism in the Lepidoptera to evolutionary biology has been
considerable. It has provided one of the best observed examples of evolutionary
change caused by natural selection and has shown that Darwinian selection can
be a strong force. In the peppered moth, differential bird predation, together
with migration, has been primarily responsible for the rise and fall of the
melanic form carbonaria.
Although the story of the peppered moth is undoubtedly more complex than usually related, data accumulated over the past 50 years have done nothing to undermine Tutt’s initial hypothesis of the role of differential bird predation or Kettlewell’s experimental demonstrations of this role.
Within the Lepidoptera, the factors responsible for melanism and the forms of melanism that result are very variable. Because a great variety of factors may promote melanism, it may be misleading to extrapolate from one population to another, let alone from one species to another. Even within one class of melanism, the relative influence of different aspects of a species’ biology will vary between species. Each species that has evolved melanic forms will have done so in the presence of a variety of different intrinsic and extrinsic circumstances. The differences in the factors affecting melanism in even the few well-studied cases suggest that there is still enormous scope for original research into this phenomenon. However, as the frequencies of dark forms of full industrial melanics decline in North America and Europe with reductions in pollution, the focus of such work may have to shift to the developing industrial nations of Asia and South America.
Although the story of the peppered moth is undoubtedly more complex than usually related, data accumulated over the past 50 years have done nothing to undermine Tutt’s initial hypothesis of the role of differential bird predation or Kettlewell’s experimental demonstrations of this role.
Within the Lepidoptera, the factors responsible for melanism and the forms of melanism that result are very variable. Because a great variety of factors may promote melanism, it may be misleading to extrapolate from one population to another, let alone from one species to another. Even within one class of melanism, the relative influence of different aspects of a species’ biology will vary between species. Each species that has evolved melanic forms will have done so in the presence of a variety of different intrinsic and extrinsic circumstances. The differences in the factors affecting melanism in even the few well-studied cases suggest that there is still enormous scope for original research into this phenomenon. However, as the frequencies of dark forms of full industrial melanics decline in North America and Europe with reductions in pollution, the focus of such work may have to shift to the developing industrial nations of Asia and South America.
