Professor, Emory University
Inside the supergene of the bird with four sexes
Abstract: The white-throated sparrow, a common backyard songbird, offers unique opportunities to understand the role of genomic architecture in alternative phenotypes. In this species, alternative plumage morphs segregate with a nonrecombining segment of chromosome 2. This autosomal rearrangement, or “supergene”, bears striking similarities to sex chromosomes. For example, homozygosity is rare and each breeding pair consists of one heterozygous individual and one individual homozygous for the standard, recombining arrangement. This species has therefore been called the “bird with four sexes”. The supergene also segregates with a behavioral phenotype—birds with it are more aggressive and less parental than birds without it. Using a combination of techniques from population genetics, molecular biology, and behavioral neuroendocrinology, we have identified at least one gene that is causal for the aggressive behavioral phenotype. We hypothesize that alleles that benefit the more aggressive strategy are accumulating inside the supergene and that additional causal genes will soon be discovered. Thus, this species provides rich possibilities for discovering alleles that work together to mediate life-history trade-offs and maximize the fitness of alternative complex phenotypes.
Host: OEB Postdocs