Meeting Abstract
Little is known about the genetic changes that enable convergent shifts in social behavior across diverse taxonomic lineages. Obligate avian brood parasitism, in which birds lay eggs in other species’ nests and rely on the ‘host’ for parental care, has evolved independently seven times in distinct lineages. This repeated loss of parental care provides a unique opportunity to reveal the molecular mechanisms responsible for the convergent evolution of behavior. To identify genes that evolved under positive selection among brood parasite lineages, we generated high coverage (> 30x) whole-genome sequences in four brood parasitic species from two distinct songbird lineages (molothrine cowbirds and viduid finches) as well as two non-parasitic relatives. Using selection tests for coding sequences (PAML), we compared over 9000 orthologous genes between brood parasites and non-parasitic songbird species. Both the cowbird and viduid finch lineages were found to have around 300 genes with significant evidence of positive selection. Many of these genes were functionally related to embryonic growth, immune system, and neuronal development. Although these genes likely represent parallel adaptations associated with brood parasitism, few genes were found to be under positive selection in both lineages. Therefore, in contrast to recent studies of gene expression that have identified relatively few genes associated with the convergent evolution of morphological traits, our results suggest that at the level of coding genes, independent changes are largely responsible for transitions to brood parasitic behavior.
