ANOLIS GENOMICS

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

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 Obiettivo del progetto (Objective)

'Understanding the evolution and maintenance of variation in observable characteristics (phenotypic variation) is a major goal in evolutionary biology. Addressing this goal requires identifying the genes responsible for important traits. Until recently, this was only possible in a handful of model species because of a lack of genomic resources in non-model organisms. But recent advances in DNA sequencing technology has revolutionized the development of genomic resources in non-model species and paved the way for major advances in gene mapping studies. Pigmentation systems are fascinating and beneficial phenotypes to consider for gene mapping, they underlie an enormous diversity of phenotypic variation, with varied functional roles. Pigmentation biology continues to play a pivotal role in developing the conceptual foundations for several areas in evolutionary biology, for example: genetics, development biology and speciation. In this project I will exploit a colour polymorphism in Anolis limifrons to identify the genes underlying variation in dewlap colour. The dewlap is an extendable flap of skin that is used for within and between species communication in anole lizards. I will sequence the transcriptome (the part of the genome that encodes proteins) to identify molecular markers and then genotype individuals of a mapping cross to map genes underlying dewlap colour variation. Anole lizards are model species in adaptive radiations, and mapping the genes responsible for dewlap colour will provide much insight into our understanding of diversification, adaptation and speciation. The study will also produce the first genetic linkage map for a lizard, thus providing much insight into the evolution of reptilian genomes. The study, which is ambitious but tractable, will provide me with valuable training and experience in gene mapping, tropical biology and speciation, and will provide me with the means to establish my independence as a research professional.'

Introduzione (Teaser)

Researchers studying the genes that control colour variation in iguanian lizards have uncovered new clues about evolution and speciation.

Descrizione progetto (Article)

Dewlaps, or throat-fans, are extendable flaps of skin beneath the chin of anole (iguanian) lizards, which they use to communicate with each other via visual displays. Dewlaps vary tremendously in size, shape and colour, but little is known about their function or why such diversity evolved.

In fact, more generally, the reason for the evolution and maintenance of such variations, known as polymorphisms, still eludes evolutionary biologists. The EU-funded ANOLIS GENOMICS project used the colour pattern variation in the dewlap of a Panamanian anole lizard to understand the genetics of colour polymorphisms.

Mapping the distribution of the Panamanian lizard's dewlap colour pattern across central Panama, researchers determined that the polymorphism has been stable over many years.

They found that although individuals from populations differing in dewlap colour can interbreed, the offspring of these crosses are less fertile. This helps to explain the maintenance of the colour pattern variation, since hybrid offspring are less likely to pass on their genes.

ANOLIS GENOMICS also determined that dewlap size is a quantitative trait, meaning there is a size distribution amongst the lizard populations. Much like height in human populations, this is caused by cumulative effects of genes and the environment.

Currently, ANOLIS GENOMICS is analysing thousands of genetic sequences for colour pattern markers, creating a genetic map to assess genetic variation between populations. Having determined that dewlap colour, pattern and size independently evolved and possibly serve different functions, researchers will see how the underlying genes contribute to speciation.

These genetic maps, along with full-genome sequences of three anole lizard species, will provide a wealth of information for the broader evolutionary genetics community.