Genes for colour variation in lizards

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.