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Elkin J, Martin A, Courtier-Orgogozo V, Santos ME. Analysis of the genetic loci of pigment pattern evolution in vertebrates. Biol Rev Camb Philos Soc 2023; 98:1250-1277. [PMID: 37017088 DOI: 10.1111/brv.12952] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/08/2023] [Accepted: 03/14/2023] [Indexed: 04/06/2023]
Abstract
Vertebrate pigmentation patterns are amongst the best characterised model systems for studying the genetic basis of adaptive evolution. The wealth of available data on the genetic basis for pigmentation evolution allows for analysis of trends and quantitative testing of evolutionary hypotheses. We employed Gephebase, a database of genetic variants associated with natural and domesticated trait variation, to examine trends in how cis-regulatory and coding mutations contribute to vertebrate pigmentation phenotypes, as well as factors that favour one mutation type over the other. We found that studies with lower ascertainment bias identified higher proportions of cis-regulatory mutations, and that cis-regulatory mutations were more common amongst animals harbouring a higher number of pigment cell classes. We classified pigmentation traits firstly according to their physiological basis and secondly according to whether they affect colour or pattern, and identified that carotenoid-based pigmentation and variation in pattern boundaries are preferentially associated with cis-regulatory change. We also classified genes according to their developmental, cellular, and molecular functions. We found a greater proportion of cis-regulatory mutations in genes implicated in upstream developmental processes compared to those involved in downstream cellular functions, and that ligands were associated with a higher proportion of cis-regulatory mutations than their respective receptors. Based on these trends, we discuss future directions for research in vertebrate pigmentation evolution.
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Affiliation(s)
- Joel Elkin
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
| | - Arnaud Martin
- Department of Biological Sciences, The George Washington University, 800 22nd St. NW, Suite 6000, Washington, DC, 20052, USA
| | | | - M Emília Santos
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
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2
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Marcondes RS. Celebrating the great avian evolutionary tradition: Review of how birds evolve, by D. J. Futuyma, Princeton & Oxford: Princeton University Press. Evolution 2022; 76:1366-1369. [PMID: 37139913 DOI: 10.1111/evo.14503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 04/07/2022] [Indexed: 11/27/2022]
Affiliation(s)
- Rafael S. Marcondes
- Museum of Natural Science and Department of Biological Sciences Louisiana State University Baton Rouge LA 70803 USA
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3
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Schwochow D, Bornelöv S, Jiang T, Li J, Gourichon D, Bed’Hom B, Dorshorst BJ, Chuong CM, Tixier-Boichard M, Andersson L. The feather pattern autosomal barring in chicken is strongly associated with segregation at the MC1R locus. Pigment Cell Melanoma Res 2021; 34:1015-1028. [PMID: 33793042 PMCID: PMC8484376 DOI: 10.1111/pcmr.12975] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 03/26/2021] [Indexed: 01/14/2023]
Abstract
Color patterns within individual feathers are common in birds but little is known about the genetic mechanisms causing such patterns. Here, we investigate the genetic basis for autosomal barring in chicken, a horizontal striping pattern on individual feathers. Using an informative backcross, we demonstrate that the MC1R locus is strongly associated with this phenotype. A deletion at SOX10, underlying the dark brown phenotype on its own, affects the manifestation of the barring pattern. The coding variant L133Q in MC1R is the most likely causal mutation for autosomal barring in this pedigree. Furthermore, a genetic screen across six different breeds showing different patterning phenotypes revealed that the most striking shared characteristics among these breeds were that they all carried the MC1R alleles Birchen or brown. Our data suggest that the presence of activating MC1R mutations enhancing pigment synthesis is an important mechanism underlying pigmentation patterns on individual feathers in chicken. We propose that MC1R and its antagonist ASIP play a critical role for determining within-feather pigmentation patterns in birds by acting as activator and inhibitor possibly in a Turing reaction-diffusion model.
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Affiliation(s)
- Doreen Schwochow
- Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden
- Université Paris-Saclay, INRAE, AgroParisTech, GABI, Jouy-en-Josas, France
| | - Susanne Bornelöv
- Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Tingxing Jiang
- Department of Pathology, University of Southern California, Los Angeles, CS, USA
| | - Jingyi Li
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA, USA
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, USA
| | | | - Bertrand Bed’Hom
- Université Paris-Saclay, INRAE, AgroParisTech, GABI, Jouy-en-Josas, France
| | - Ben J. Dorshorst
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA, USA
| | - Cheng-Ming Chuong
- Department of Pathology, University of Southern California, Los Angeles, CS, USA
| | | | - Leif Andersson
- Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden
- Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, USA
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4
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Janssen K, Bustnes JO, Mundy NI. Variation in Genetic Mechanisms for Plumage Polymorphism in Skuas (Stercorarius). J Hered 2021; 112:430-435. [PMID: 34343335 PMCID: PMC8634071 DOI: 10.1093/jhered/esab038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 06/28/2021] [Indexed: 11/13/2022] Open
Abstract
Coloration is evolutionarily labile and so provides an excellent trait for examining the repeatability of evolution. Here, we investigate the repeatability of the evolution of polymorphic variation in ventral plumage coloration in skuas (Stercorarius: Stercorariidae). In 2 species, arctic (S. parasiticus) and pomarine skuas (S. pomarinus), plumage polymorphism was previously shown to be associated with coding changes at the melanocortin-1 receptor (MC1R) locus. Here, we show that polymorphism in a third species, the south polar skua (S. maccormicki), is not associated with coding variation at MC1R or with variation at a Z-linked second candidate locus, tyrosinase-related protein 1 (TYRP1). Hence, convergent evolution of plumage polymorphisms in skuas is only partly repeatable at the level of the genetic locus involved. Interestingly, the pattern of repeatability in skuas is aligned not with phylogeny but with the nature of the phenotypic variation. In particular, south polar skuas show a strong sex bias to coloration that is absent in the other species, and it may be that this has a unique genetic architecture.
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Affiliation(s)
- Kirstin Janssen
- Department of Natural Sciences, Tromsø University Museum, NO-9037 Tromsø, Norway.,Centre of Forensic Genetics, Institute of Medical Biology, Faculty of Health Sciences, UIT The Arctic University of Norway, NO-9037 Tromsø, Norway
| | - Jan Ove Bustnes
- Norwegian Institute for Nature Research, The Fram Centre, NO-9296 Tromsø,Norway
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5
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Posso-Terranova A, Andrés J. Skin transcriptional profiles in Oophaga poison frogs. Genet Mol Biol 2020; 43:e20190401. [PMID: 33211057 PMCID: PMC7678260 DOI: 10.1590/1678-4685-gmb-2019-0401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 06/06/2020] [Indexed: 12/03/2022] Open
Abstract
Aposematic organisms advertise their defensive toxins to predators using a variety of warning
signals, including bright coloration. While most Neotropical poison frogs (Dendrobatidae) rely on
crypsis to avoid predators, Oophaga poison frogs from South America advertise their
chemical defenses, a complex mix of diet-derived alkaloids, by using conspicuous hues. The present
study aimed to characterize the skin transcriptomic profiles of South American
Oophaga poison frogs. Our analyses showed very similar transcriptomic profiles for
these closely related species in terms of functional annotation and relative abundance of gene
ontology terms expressed. Analyses of expression profiles of Oophaga and available
skin transcriptomes of cryptic anurans allowed us to propose initial hypotheses for the active
sequestration of alkaloid-based chemical defenses and to highlight some genes that may be
potentially involved in resistance mechanisms to avoid self-intoxication and skin coloration. In
doing so, we provide an important molecular resource for the study of warning signals that will
facilitate the assembly and annotation of future poison frog genomes.
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Affiliation(s)
- Andrés Posso-Terranova
- University of Saskatchewan, Department of Biology, Saskatoon, SK, Canada.,Universidad Nacional de Colombia sede Palmira, Palmira, Colombia
| | - José Andrés
- University of Saskatchewan, Department of Biology, Saskatoon, SK, Canada.,Cornell University, Department of Ecology and Evolution, Ithaca, NY, USA
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6
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Posso-Terranova A, Andrés JÁ. Diversification and convergence of aposematic phenotypes: truncated receptors and cellular arrangements mediate rapid evolution of coloration in harlequin poison frogs. Evolution 2017; 71:2677-2692. [DOI: 10.1111/evo.13335] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 07/28/2017] [Accepted: 08/10/2017] [Indexed: 12/26/2022]
Affiliation(s)
- Andrés Posso-Terranova
- Department of Biology; University of Saskatchewan; 112 Science Pl Saskatoon SK Canada
- Facultad de Ciencias Agropecuarias; Universidad Nacional de Colombia; Sede de Palmira A.A. 237 Palmira Colombia
| | - José Á. Andrés
- Department of Biology; University of Saskatchewan; 112 Science Pl Saskatoon SK Canada
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Tang QY, Shi LX, Liu F, Yu D, Liu HZ. Evolution and phylogenetic application of the MC1R gene in the Cobitoidea (Teleostei: Cypriniformes). Zool Res 2017; 37:281-9. [PMID: 27686787 DOI: 10.13918/j.issn.2095-8137.2016.5.281] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Fish of the superfamily Cobitoidea sensu stricto (namely loaches) exhibit extremely high diversity of color patterns, but so far little is known about their evolutionary mechanism. Melanocortin 1 receptor gene (MC1R) plays an important role during the synthesis of melanin and formation of animal body color patterns. In this study, we amplified and sequenced the partial MC1R gene for 44 loach individuals representing 31 species of four families. Phylogenetic analyses yielded a topology congruent with previous studies using multiple nuclear loci, showing that each of the four families was monophyletic with sister relationships of Botiidae+ (Cobitidae+(Balitoridae+Nemacheilidae)). Gene evolutionary analyses indicated that MC1R in loaches was under purifying selection pressure, with various sites having different dN/dS values. Both Botiidae and Cobitidae had lower dN/dS values than those of background lineages, suggesting their evolution might be strongly affected by purifying selection pressure. For Balitoridae and Nemacheilidae, both had larger dN/dS values than those of background lineages, suggesting they had a faster evolutionary rate under more relaxed selection pressure. Consequently, we inferred that the relatively stable color patterns in Botiidae and Cobitidae might result from the strong purifying selection pressure on the MC1R gene, whereas the complicated and diverse color patterns in Balitoridae and Nemacheilidae might be associated with the relaxed selection pressure. Given the easy experimental procedure for the partial MC1R gene and its excellent performance in reconstructing phylogeny, we suggest this gene could be used as a good molecular marker for the phylogenetic study of fish species.
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Affiliation(s)
- Qiong-Ying Tang
- The Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
| | - Li-Xia Shi
- The Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China;University of Chinese Academy of Sciences, Beijing 100049, China
| | - Fei Liu
- The Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Dan Yu
- The Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Huan-Zhang Liu
- The Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
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8
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Corso J, Mundy NI, Fagundes NJR, de Freitas TRO. Evolution of dark colour in toucans (Ramphastidae): a case of molecular adaptation? J Evol Biol 2016; 29:2530-2538. [PMID: 27654325 DOI: 10.1111/jeb.12982] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 08/08/2016] [Accepted: 09/16/2016] [Indexed: 11/28/2022]
Abstract
In the last decades, researchers have been able to determine the molecular basis of some phenotypes, to test for evidence of natural selection upon them, and to demonstrate that the same genes or genetic pathways can be associated with convergent traits. Colour traits are often subject to natural selection because even small changes in these traits can have a large effect on fitness via camouflage, sexual selection or other mechanisms. The melanocortin-1 receptor locus (MC1R) is frequently associated with intraspecific coat colour variation in vertebrates, but it has been far harder to demonstrate that this locus is involved in adaptive interspecific colour differences. Here, we investigate the contribution of the MC1R gene to the colour diversity found in toucans (Ramphastidae). We found divergent selection on MC1R in the clade represented by the genus Ramphastos and that this coincided with the evolution of darker plumage in members of this genus. Using phylogenetically corrected correlations, we show significant and specific relationships between the rate of nonsynonymous change in MC1R (dN) and plumage darkness across Ramphastidae, and also between the rate of functionally significant amino acid changes in MC1R and plumage darkness. Furthermore, three of the seven amino acid changes in MC1R that occurred in the ancestral Ramphastos branch are associated with melanism in other birds. Taken together, our results suggest that the dark colour of Ramphastos toucans was related to nonsynonymous substitutions in MC1R that may have been subject to positive selection or to a relaxation of selective pressure. These results also demonstrate a quantitative relationship between gene and phenotype evolution, representing an example of how MC1R molecular evolution may affect macroevolution of plumage phenotypes.
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Affiliation(s)
- J Corso
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - N I Mundy
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - N J R Fagundes
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.,Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - T R O de Freitas
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.,Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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9
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San-Jose LM, Ducrest AL, Ducret V, Béziers P, Simon C, Wakamatsu K, Roulin A. Effect of the MC1R gene on sexual dimorphism in melanin-based colorations. Mol Ecol 2015; 24:2794-808. [PMID: 25857339 DOI: 10.1111/mec.13193] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 03/27/2015] [Accepted: 03/31/2015] [Indexed: 02/04/2023]
Abstract
Variants of the melanocortin-1 receptor (MC1R) gene result in abrupt, naturally selected colour morphs. These genetic variants may differentially affect sexual dimorphism if one morph is naturally selected in the two sexes but another morph is naturally or sexually selected only in one of the two sexes (e.g. to confer camouflage in reproductive females or confer mating advantage in males). Therefore, the balance between natural and sexual selections can differ between MC1R variants, as suggest studies showing interspecific correlations between sexual dimorphism and the rate of nonsynonymous vs. synonymous amino acid substitutions at the MC1R. Surprisingly, how MC1R is related to within-species sexual dimorphism, and thereby to sex-specific selection, has not yet been investigated. We tackled this issue in the barn owl (Tyto alba), a species showing pronounced variation in the degree of reddish pheomelanin-based coloration and in the number and size of black feather spots. We found that a valine (V)-to-isoleucine (I) substitution at position 126 explains up to 30% of the variation in the three melanin-based colour traits and in feather melanin content. Interestingly, MC1R genotypes also differed in the degree of sexual colour dimorphism, with individuals homozygous for the II MC1R variant being 2 times redder and 2.5 times less sexually dimorphic than homozygous individuals for the VV MC1R variant. These findings support that MC1R interacts with the expression of sexual dimorphism and suggest that a gene with major phenotypic effects and weakly influenced by variation in body condition can participate in sex-specific selection processes.
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Affiliation(s)
- Luis M San-Jose
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, CH-1015, Lausanne, Switzerland
| | - Anne-Lyse Ducrest
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, CH-1015, Lausanne, Switzerland
| | - Valérie Ducret
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, CH-1015, Lausanne, Switzerland
| | - Paul Béziers
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, CH-1015, Lausanne, Switzerland
| | - Céline Simon
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, CH-1015, Lausanne, Switzerland
| | - Kazumasa Wakamatsu
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi, 470-1192, Japan
| | - Alexandre Roulin
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, CH-1015, Lausanne, Switzerland
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10
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Li L, Li D, Liu L, Li S, Feng Y, Peng X, Gong Y. Endothelin Receptor B2 (EDNRB2) Gene Is Associated with Spot Plumage Pattern in Domestic Ducks (Anas platyrhynchos). PLoS One 2015; 10:e0125883. [PMID: 25955279 PMCID: PMC4425580 DOI: 10.1371/journal.pone.0125883] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 03/08/2015] [Indexed: 01/24/2023] Open
Abstract
Endothelin receptor B subtype 2 (EDNRB2) is a seven-transmembrane G-protein coupled receptor. In this study, we investigated EDNRB2 gene as a candidate gene for duck spot plumage pattern according to studies of chicken and Japanese quail. The entire coding region was cloned by the reverse transcription polymerase chain reaction (RT-PCR). Sequence analysis showed that duck EDNRB2 cDNA contained a 1311bp open reading frame and encoded a putative protein of 436 amino acids residues. The transcript shared 89%-90% identity with the counterparts in other avian species. A phylogenetic tree based on amino acid sequences showed that duck EDNRB2 was evolutionary conserved in avian clade. The entire coding region of EDNRB2 were sequenced in 20 spot and 20 non-spot ducks, and 13 SNPs were identified. Two of them (c.940G>A and c.995G>A) were non-synonymous substitutions, and were genotyped in 647 ducks representing non-spot and spot phenotypes. The c.995G>A mutation, which results in the amino acid substitution of Arg332His, was completely associated with the spot phenotype: all 152 spot ducks were carriers of the AA genotype and the other 495 individuals with non-spot phenotype were carriers of GA or GG genotype, respectively. Segregation in 17 GA×GG and 22 GA×GA testing combinations confirmed this association since the segregation ratios and genotypes of the offspring were in agreement with the hypothesis. In order to investigate the underlying mechanism of the spot phenotype, MITF gene was used as cell type marker of melanocyte progenitor cells while TYR and TYRP1 gene were used as cell type markers of mature melanocytes. Transcripts of MITF, TYR and TYRP1 gene with expected size were identified in all pigmented skin tissues while PCR products were not obtained from non-pigmented skin tissues. It was inferred that melanocytes are absent in non-pigmented skin tissues of spot ducks.
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Affiliation(s)
- Ling Li
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Dan Li
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Li Liu
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Shijun Li
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Yanping Feng
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Xiuli Peng
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Yanzhang Gong
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
- * E-mail:
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11
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Roulin A, Ducrest AL. Genetics of colouration in birds. Semin Cell Dev Biol 2013; 24:594-608. [PMID: 23665152 DOI: 10.1016/j.semcdb.2013.05.005] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2012] [Revised: 04/19/2013] [Accepted: 05/01/2013] [Indexed: 01/01/2023]
Abstract
Establishing the links between phenotype and genotype is of great importance for resolving key questions about the evolution, maintenance and adaptive function of phenotypic variation. Bird colouration is one of the most studied systems to investigate the role of natural and sexual selection in the evolution of phenotypic diversity. Given the recent advances in molecular tools that allow discovering genetic polymorphisms and measuring gene and protein expression levels, it is timely to review the literature on the genetics of bird colouration. The present study shows that melanin-based colour phenotypes are often associated with mutations at melanogenic genes. Differences in melanin-based colouration are caused by switches of eumelanin to pheomelanin production or by changes in feather keratin structure, melanoblast migration and differentiation, as well as melanosome structure. Similar associations with other types of colourations are difficult to establish, because our knowledge about the molecular genetics of carotenoid-based and structural colouration is quasi inexistent. This discrepancy stems from the fact that only melanin-based colouration shows pronounced heritability estimates, i.e. the resemblance between related individuals is usually mainly explained by genetic factors. In contrast, the expression of carotenoid-based colouration is phenotypically plastic with a high sensitivity to variation in environmental conditions. It therefore appears that melanin-based colour traits are prime systems to understand the genetic basis of phenotypic variation. In this context, birds have a great potential to bring us to new frontiers where many exciting discoveries will be made on the genetics of phenotypic traits, such as colouration. In this context, a major goal of our review is to suggest a number of exciting future avenues.
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Affiliation(s)
- Alexandre Roulin
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
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