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Color Variation (color + variation)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

ADAPTIVE REPTILE COLOR VARIATION AND THE EVOLUTION OF THE MCIR GENE

EVOLUTION, Issue 8 2004
Erica Bree Rosenblum
Abstract The wealth of information on the genetics of pigmentation and the clear fitness consequences of many pigmentation phenotypes provide an opportunity to study the molecular basis of an ecologically important trait. The melanocortin-1 receptor (Mc1r) is responsible for intraspecific color variation in mammals and birds. Here, we study the molecular evolution of Mc1r and investigate its role in adaptive intraspecific color differences in reptiles. We sequenced the complete Mc1r locus in seven phylogenetically diverse squamate species with melanic or blanched forms associated with different colored substrates or thermal environments. We found that patterns of amino acid substitution across different regions of the receptor are similar to the patterns seen in mammals, suggesting comparable levels of constraint and probably a conserved function for Mc1r in mammals and reptiles. We also found high levels of silent-site heterozygosity in all species, consistent with a high mutation rate or large long-term effective population size. Mc1r polymorphisms were strongly associated with color differences in Holbrookia maculata and Aspidoscelis inornata. In A. inornata, several observations suggest that Mc1r mutations may contribute to differences in color: (1) a strong association is observed between one Mc1r amino acid substitution and dorsal color; (2) no significant population structure was detected among individuals from these populations at the mitochondrial ND4 gene; (3) the distribution of allele frequencies at Mc1r deviates from neutral expectations; and (4) patterns of linkage disequilibrium at Mc1r are consistent with recent selection. This study provides comparative data on a nuclear gene in reptiles and highlights the utility of a candidate-gene approach for understanding the evolution of genes involved in vertebrate adaptation. [source]

EVOLUTION OF COLOR VARIATION IN DRAGON LIZARDS: QUANTITATIVE TESTS OF THE ROLE OF CRYPSIS AND LOCAL ADAPTATION

EVOLUTION, Issue 7 2004
Devi M. Stuart-Fox
Abstract Many animal species display striking color differences with respect to geographic location, sex, and body region. Traditional adaptive explanations for such complex patterns invoke an interaction between selection for conspicuous signals and natural selection for crypsis. Although there is now a substantial body of evidence supporting the role of sexual selection for signaling functions, quantitative studies of crypsis remain comparatively rare. Here, we combine objective measures of coloration with information on predator visual sensitivities to study the role of crypsis in the evolution of color variation in an Australian lizard species complex (Ctenophorus decresii). We apply a model that allows us to quantify crypsis in terms of the visual contrast of the lizards against their natural backgrounds, as perceived by potential avian predators. We then use these quantitative estimates of crypsis to answer the following questions. Are there significant differences in crypsis conspicuousness among populations? Are there significant differences in crypsis conspicuousness between the sexes? Are body regions "exposed" to visual predators more cryptic than "hidden" body regions? Is there evidence for local adaptation with respect to crypsis against different substrates? In general, our results confirmed that there are real differences in crypsis conspicuousness both between populations and between sexes; that exposed body regions were significantly more cryptic than hidden ones, particularly in females; and that females, but not males, are more cryptic against their own local background than against the background of other populations. Body regions that varied most in contrast between the sexes and between populations were also most conspicuous and are emphasized by males during social and sexual signaling. However, results varied with respect to the aspect of coloration studied. Results based on chromatic contrast ("hue' of color) provided better support for the crypsis hypothesis than did results based on achromatic contrast ("brightness' of color). Taken together, these results support the view that crypsis plays a substantial role in the evolution of color variation and that color patterns represent a balance between the need for conspicuousness for signaling and the need for crypsis to avoid predation. [source]

Taxonomic Study of Korean Cantharidae (Coleoptera) V. A Newly Recorded Genus and Species, Pseudoabsidia ussurica Wittmer, from Korea

ENTOMOLOGICAL RESEARCH, Issue 1 2002
Tau KANG
ABSTRACT We examined newly recorded species, Pseudoabsidia ussurica Wittmer, from Korea. The species was redescribed with their color variation. Also, the photos of adult habitus and aedeagus are provided. [source]

ADAPTIVE REPTILE COLOR VARIATION AND THE EVOLUTION OF THE MCIR GENE

EVOLUTION, Issue 8 2004
Erica Bree Rosenblum
Abstract The wealth of information on the genetics of pigmentation and the clear fitness consequences of many pigmentation phenotypes provide an opportunity to study the molecular basis of an ecologically important trait. The melanocortin-1 receptor (Mc1r) is responsible for intraspecific color variation in mammals and birds. Here, we study the molecular evolution of Mc1r and investigate its role in adaptive intraspecific color differences in reptiles. We sequenced the complete Mc1r locus in seven phylogenetically diverse squamate species with melanic or blanched forms associated with different colored substrates or thermal environments. We found that patterns of amino acid substitution across different regions of the receptor are similar to the patterns seen in mammals, suggesting comparable levels of constraint and probably a conserved function for Mc1r in mammals and reptiles. We also found high levels of silent-site heterozygosity in all species, consistent with a high mutation rate or large long-term effective population size. Mc1r polymorphisms were strongly associated with color differences in Holbrookia maculata and Aspidoscelis inornata. In A. inornata, several observations suggest that Mc1r mutations may contribute to differences in color: (1) a strong association is observed between one Mc1r amino acid substitution and dorsal color; (2) no significant population structure was detected among individuals from these populations at the mitochondrial ND4 gene; (3) the distribution of allele frequencies at Mc1r deviates from neutral expectations; and (4) patterns of linkage disequilibrium at Mc1r are consistent with recent selection. This study provides comparative data on a nuclear gene in reptiles and highlights the utility of a candidate-gene approach for understanding the evolution of genes involved in vertebrate adaptation. [source]

EVOLUTION OF COLOR VARIATION IN DRAGON LIZARDS: QUANTITATIVE TESTS OF THE ROLE OF CRYPSIS AND LOCAL ADAPTATION

EVOLUTION, Issue 7 2004
Devi M. Stuart-Fox
Abstract Many animal species display striking color differences with respect to geographic location, sex, and body region. Traditional adaptive explanations for such complex patterns invoke an interaction between selection for conspicuous signals and natural selection for crypsis. Although there is now a substantial body of evidence supporting the role of sexual selection for signaling functions, quantitative studies of crypsis remain comparatively rare. Here, we combine objective measures of coloration with information on predator visual sensitivities to study the role of crypsis in the evolution of color variation in an Australian lizard species complex (Ctenophorus decresii). We apply a model that allows us to quantify crypsis in terms of the visual contrast of the lizards against their natural backgrounds, as perceived by potential avian predators. We then use these quantitative estimates of crypsis to answer the following questions. Are there significant differences in crypsis conspicuousness among populations? Are there significant differences in crypsis conspicuousness between the sexes? Are body regions "exposed" to visual predators more cryptic than "hidden" body regions? Is there evidence for local adaptation with respect to crypsis against different substrates? In general, our results confirmed that there are real differences in crypsis conspicuousness both between populations and between sexes; that exposed body regions were significantly more cryptic than hidden ones, particularly in females; and that females, but not males, are more cryptic against their own local background than against the background of other populations. Body regions that varied most in contrast between the sexes and between populations were also most conspicuous and are emphasized by males during social and sexual signaling. However, results varied with respect to the aspect of coloration studied. Results based on chromatic contrast ("hue' of color) provided better support for the crypsis hypothesis than did results based on achromatic contrast ("brightness' of color). Taken together, these results support the view that crypsis plays a substantial role in the evolution of color variation and that color patterns represent a balance between the need for conspicuousness for signaling and the need for crypsis to avoid predation. [source]

The evolution of black plumage from blue in Australian fairy-wrens (Maluridae): genetic and structural evidence

JOURNAL OF AVIAN BIOLOGY, Issue 5 2010
Amy C. Driskell
Genetic variation in the melanocortin-1 receptor (MC1R) locus is responsible for color variation, particularly melanism, in many groups of vertebrates. Fairy-wrens, Maluridae, are a family of Australian and New Guinean passerines with several instances of dramatic shifts in plumage coloration, both intra- and inter-specifically. A number of these color changes are from bright blue to black plumage. In this study, we examined sequence variation at the MC1R locus in most genera and species of fairy-wrens. Our primary focus was subspecies of the white-winged fairy-wren Malurus leucopterus in which two subspecies, each endemic to islands off the western Australian coast, are black while the mainland subspecies is blue. We found fourteen variable amino acid residues within M. leucopterus, but at only one position were alleles perfectly correlated with plumage color. Comparison with other fairy-wren species showed that the blue mainland subspecies, not the black island subspecies, had a unique genotype. Examination of MC1R protein sequence variation across our sample of fairy-wrens revealed no correlation between plumage color and sequence in this group. We thus conclude that amino acid changes in the MC1R locus are not directly responsible for the black plumage of the island subspecies of M. leucopterus. Our examination of the nanostructure of feathers from both black and blue subspecies of M. leucopterus and other black and blue fairy-wren species clarifies the evolution of black plumage in this family. Our data indicate that the black white-winged fairy-wrens evolved from blue ancestors because vestiges of the nanostructure required for the production of blue coloration exist within their black feathers. Based on our phylogeographic analysis of M. leucopterus, in which the two black subspecies do not appear to be each other's closest relatives, we infer that there have been two independent evolutionary transitions from blue to black plumage. A third potential transition from blue to black appears to have occurred in a sister clade. [source]

Floral color patterns in a tropical orchid: Are they associated with reproductive success?

PLANT SPECIES BIOLOGY, Issue 2 2007
RAYMOND L. TREMBLAY
Abstract We sought to measure phenotypic selection on petal color variation in populations of Lepanthes rupestris, a diminutive epilithic orchid of Puerto Rico that exhibits a polymorphism in petal color patterns (unicolor or bicolored). We censused seven populations monthly for 20 months and noted flower production and petal color pattern. Each flower was checked for pollinarium removal (male fitness measure) and fruit production (female fitness). In all populations, plants with bicolored petals dominated and comprised 63,82% of individuals. Aside from petal color differences, the two types were indistinguishable. Flower color pattern was generally not associated with either male or female reproductive success within or among populations or over time. Environmental conditions, rainfall and humidity, may account for both temporal and spatial variation in the reproductive success observed among sites. Although we were unable to tag fitness to petal color patterns, the consistent ratio of color morphs among populations suggests that factors other than just drift are responsible for the frequencies we observed. [source]

Race and global patterns of phenotypic variation

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2009
John H. Relethford
Abstract Phenotypic traits have been used for centuries for the purpose of racial classification. Developments in quantitative population genetics have allowed global comparison of patterns of phenotypic variation with patterns of variation in classical genetic markers and DNA markers. Human skin color shows a high degree of variation among geographic regions, typical of traits that show extensive natural selection. Even given this high level of geographic differentiation, skin color variation is clinal and is not well described by discrete racial categories. Craniometric traits show a level of among-region differentiation comparable to genetic markers, with high levels of variation within populations as well as a correlation between phenotypic and geographic distance. Craniometric variation is geographically structured, allowing high levels of classification accuracy when comparing crania from different parts of the world. Nonetheless, the boundaries in global variation are not abrupt and do not fit a strict view of the race concept; the number of races and the cutoffs used to define them are arbitrary. The race concept is at best a crude first-order approximation to the geographically structured phenotypic variation in the human species. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. [source]

Variation of the melanocortin 1 receptor gene in the macaques

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 8 2008
Kazuhiro Nakayama
Abstract Melanocortin 1 receptor (MC1R), a G-coupled seven-transmembrane receptor protein, plays a key role in the regulation of melanin synthesis in mammals. Sequence variation of the MC1R gene (MC1R) has been associated with pigmentation phenotypes in humans and in several animal species. The macaques (genus Macaca) are known to show a marked inter-specific variation in coat color although the causative genetic variation remains unclear. We investigated nucleotide sequences of the MC1R in 67 individuals of 18 macaque species with different coat color phenotypes including black and agouti. Twenty-eight amino acid replacements were identified in the macaques, but none of these amino acid replacements could explain the black coat color of Macaca silenus and the Sulawesi macaque species. Our molecular evolutionary analysis has revealed that nonsynonymous substitution/synonymous substitution (dN/dS) ratio of the MC1R has not been uniform in the macaque groups and, moreover, their coat color and dN/dS ratio were not related. These results suggest that the MC1R is unlikely to be responsible for the coat color variation of the macaques and functions of MC1R other than pigmentation might be associated with the different selective pressures on the MC1R in macaques. Am. J. Primatol. 70:778,785, 2008. © 2008 Wiley-Liss, Inc. [source]