Genomic basis of evolutionary radiation in Lake Malawi cichlids

Abstract

Understanding the genomic basis and origin of phenotypic variation is one of the fundamental questions of biology. Evolutionary radiations characterized by a range of natural phenotypic variants between genetically closely related species are a great model to study the origin and genetic mechanisms underlying phenotypic diversity. I use one such model, cichlids from Lake Malawi to understand the basis of complex behavior evolution. Lake Malawi cichlids are broadly divided into rock dwelling and sand dwelling lineages based on the habitat they colonize in the lake. Within this split on the basis of habitat comes a wide range of behavioral differences that define rock dweller and sand dweller cichlids. Within the sand dweller lineage, males build species specific bowers to attract females in seasonal leks. Whole genomes from 28 different cichlid species from Lake Malawi were used to show that: (a) Most of the variation segregating rock dwelling cichlids from sand dwelling cichlids is in functional regions in the genome, associated with genes and pathways related to early brain development and adult behavior and (b) Bower building behavior has repeatedly evolved via with polygenic selection on ancient and new genetic variants associated with genes and pathways involved in neural activity.