Meeting Abstract
Chromosomal inversions are thought to contribute to adaptation and speciation as they reduce recombination, protecting favorable combinations of alleles. White-throated sparrows Zonotrichia albicollis are a remarkable species in which a large inversion on chromosome two is perfectly associated with a suite of behavioral and morphological characteristics that define two “morphs” within the species. This polymorphic inversion, in combination with dissasortative mating, leads to the stable maintenance of the two morphs within the species. Among the behavioral traits that vary predictably by morph are key aspects of social behavior including levels of aggression and parental care in both sexes. The unique features of this system have made white-throated sparrows a model system for the study of social behavior. With this is mind, we sequenced and assembled the genome of this species. Doing so, in combination with pooled whole genome resequencing and phylogenomic approaches, enabled us to resolve the evolutionary and demographic history of the inversion. As expected, we find high levels of divergence between the two chromosomal morphs including divergence in multiple candidate genes for behavioral variation. Because one of the two alleles exists in a perpetually non-recombining state, we also find evidence of degradation, akin to Y and W sex chromosomes. Lastly, we find dramatically reduced polymorphism across the inverted chromosomes, a pattern likely attributed to enhanced purifying selection.
