Evolution 2016: Using Genomic Tools to Explore Selection and Evolution in Anolis Species

By Pavitra Muralidhar

Adaptive radiation is one of the most intriguing processes in evolutionary biology, and anoles are one of the well-studied examples of this process. Anoles have diversified into over 400 species across the Caribbean and Central America, and contain a multitude of highly divergent morphological and behavioral types. Thanks to an impressive history of research on this clade, we now know quite a lot about the phenotypic aspects of this adaptive radiation; however, we still don’t have a good understanding of the genetic mechanisms underlying this diversity of form, physiology, and behavior. The recent advent of next-generation sequencing, and thus the ability to quickly sequence entire genomes of non-model organisms, offers a tantalizing possibility for investigating the genetic basis of adaptive radiation in Anolis.

Tollis et al., in a lightning talk at Evolution, take advantage of these new genome-sequencing techniques to approach the genetics of adaptive radiation in Anolis. To understand the genetic mechanisms underlying the adaptive radiation of anoles, they preformed de novo genome sequencing on three Anolis species (Anolis frenatus, Anolis apletophallus, and Anolis auratus), chosen to capture different sub-groups of the Anolis phylogeny. With these data, and the published genome sequence of Anolis carolinensis, they looked for patterns in the rate of evolution compared to other vertebrate groups. They also looked within the Anolis genome to detect specific genetic regions associated with selection across the anole radiation.

Tollis et al. found that, in general, anoles appear to have a high rate of molecular evolution for a vertebrate species, which may parallel the high rate of phenotypic evolution seen in this clade. In addition, Tollis et al. looked for signatures of selection across the four Anolis genomes and identified regions associated with reproduction, olfactory reception, and limb development. This last category is of special interest, given that anoles are notorious for changes in limb morphology between species and that limb morphology is one of the key components of ectomorphs in the Greater Antilles. Tollis et al. have provided a great example of using new genetic tools to approach fundamental questions about the mechanisms underlying adaptive radiation.