ANOLIS GENOMICS · Identification of genes underlying a colour polymorphism in Anolis lizards using next generation transcriptome sequencing and SNP genotyping

Identification of genes underlying a colour polymorphism in Anolis lizards using next generation transcriptome sequencing and SNP genotyping.

Colour polymorphisms have long fascinated biologists - not only because they represent spectacular variation in animal colour, but importantly because their maintenance poses important questions in evolutionary biology. Studies of colour polymorphisms have provided enormous insight into factors governing the maintenance of phenotypic variation and processes of speciation. In a Panamanian lizard (Anolis apletophallus) there exists a colour-pattern polymorphism in the throat fan, or dewlap, that provides an ideal opportunity to understand the evolution of colour polymorphisms. The main objective of this project was to determine the mode of inheritance and map the genes that control dewlap colour pattern. The main results achieved so far have provided important insight into the evolution of this colour-pattern polymorphism. I have mapped the distribution of the dewlap colour-pattern across central Panama. By comparing the results of current surveys with historical records I determined that the polymorphism has been stable over the last 35 years. I have collaborated with researchers at the University of Nottingham to investigate how colour-pattern is related to environmental variables (temperature, rainfall) using species distribution modeling. Our results suggest that colour-pattern is no related to environmental gradients. I have written a draft of this manuscript. I have also identified the mode of inheritance of dewlap morphological traits; colour-pattern is a mendelian-dominant trait and dewlap size is a heritable quantitative trait. I have shown that individuals from different populations differing in dewlap colour pattern can interbreed and the offspring of these crosses are viable, but suffer lower fertility. Lower hybrid fertility could reduce gene flow between populations and help to explain how phenotypic differences are maintained between populations. I have drafted a manuscript describing these results. The final phase of the project is to analyse the genetic data and prepare the results for publication. The population-genetic data is currently being analysed. I have identified over 10,000 genetic markers (single nucleotide polymorphisms or SNPs). These will be used to perform a genome-wise association scan to identify the SNPs associated with the colour-pattern. The data will also be useful to examine the genetic variation between populations and make inference about the historical demography of these populations. I have also prepared pedigree-genetic data. This data will be used to build a genetic linkage map to order the SNPs on the genome. With collaborators at Arizona State University, we have sequenced the genomes of three species of anole, including A. apletophallus. These genome sequences will provide genomic insights into the spectacular radiation of Anolis lizards and be a valuable genomic resource to the broader comparative genomic community. I will use these genome sequences to look for signatures of selection in candidate pigmentation genes. The results of this project are set to make an important contribution to the field, I have demonstrated that colour, pattern and size have different genetic architectures, are under different selective pressure and evolved independently, which helps to explain the great diversity in dewlaps we see across the Anole lizard genus. With knowledge of the genes underlying dewlap colour pattern I can assess if these genes have been under selection in this polymorphic species and relate this to speciation in Anoles. The genetic linkage map that I will create will be the first genetic linkage map for a lizard, and combined with the genome sequence will provide an opportunity to investigate the degree of synteny with Anolis carolinensis, and the first glimpse of degree of genomic rearrangement within the genus. This will have important implications for future genome sequencing projects and genetic mapping studies in the genus.

Data: CORDIS, © European Union