Presentation Detail

Genetics of Adaptation

Crawford, Nicholas [1], McGreevy, Jr., Thomas [1], Mullen, Sean [1], Schneider, Christopher [1].

Genomics of local adaptation and colorful pigmentation in Anolis lizards.

Understanding how the genome evolves as populations adapt to their environments is a fundamental question in evolutionary biology. Work in early diverging populations has revealed that regions of divergence evolve in discreet clusters along the genome. There is evidence that these clusters, or islands of divergence, are often found near centromeres, within inversions, or on sex chromosomes. This suggests that a combination of selection and reduced recombination is driving divergence and local adaptation.To investigate whether these mechanisms are involved in the early divergence of anolis lizards, one of the most specious groups of terrestrial vertebrates, we sampled two populations of the leopard anole (Anolis marmoratus). The populations are little differentiated genetically (mean F_ST = 0.089), but phenotypically they are distinct, with males in one population having blue heads and the males in the other having orange spotted heads. The populations also inhabit different environments: one is found in coastal rainforest while the other is found in coastal scrub woodland. It is likely the phenotypic differences are maintained by a combination of divergent natural and sexual selection.To study how these differences evolved from a genomic perspective, we sequenced complete genomes of ten males from each population at an average of 1.4x coverage per individual. We identified ca. 7.6 million single nucleotide variants (SNVs) in a comparison between the two populations. Using windowed measures of F_ST, Tajima’s D, and linkage disequilibrium (LD) we identified five genomic regions that are likely to contain adaptive loci. The five regions show higher than expected divergence among populations and, within populations, evidence of purifying selection and increased LD. Several candidate genes that affect skin pigmentation are contained within these regions and may be causally related to the observed phenotypic variation among populations.

1 - Boston University, Biology, 5 Cummington Mall, Boston, MA, 02215, USA

Keywords:
bulk-segregant
selection scan
Speciation
Adaptation
pigmentation.

Presentation Type: Regular Oral Presentation
Session: 137
Location: Rendezvous A/Snowbird Center
Date: Tuesday, June 25th, 2013
Time: 10:30 AM
Number: 137001
Abstract ID:71
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation