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New research shows how alternative 'supergene' alleles of Estrogen Receptor 1 are differentially expressed in specific brain nuclei causing aggressive behavior in the white-throated sparrow., (Published by Elsevier Inc.)

How does a naive, young animal decide from which adults to learn behavior? Obligate brood parasitic birds, including brown-headed cowbirds (Molothrus ater), face a particular challenge in learning species-specific behaviors; they lay their eggs in the nest of another species, and juveniles are raised without exposure to adult conspecifics. Nevertheless, male cowbirds need to learn a conspecific song to attract appropriate mates, and female cowbirds need to learn to identify conspecific males for mating. Traditionally, it was thought that parasitic bird species rely purely on instinctual species recognition [1-4], but an alternative is that a species-specific trait serves as a "password" [5], a non-learned cue for naive animals that guides decisions regarding from whom to learn. Here, we tested the hypothesis that the adult "chatter call" enhances the learning of specific songs in juvenile cowbirds. We exposed acoustically naive juvenile male and female cowbirds to songs paired with chatter calls and found that the chatter call enhanced song production learning in males and induced a neurogenomic profile of song familiarity in females, even for heterospecific songs. Thus, a combination of experience-independent and -dependent mechanisms converges to explain how young cowbirds emerge from another species' nest yet learn behaviors from conspecifics. Identifying whether such password-based mechanisms relate to perceptual and behavioral learning in non-parasitic taxa will contribute to our general understanding of the development of social recognition systems., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

A major challenge in biology is to understand the genetic basis of adaptation. One compelling idea is that groups of tightly linked genes (i.e., "supergenes" [1, 2]) facilitate adaptation in suites of traits that determine fitness. Despite their likely importance, little is known about how alternate supergene alleles arise and become differentiated, nor their ultimate fate within species. Herein we address these questions by investigating the evolutionary history of a supergene in white-throated sparrows, Zonotrichia albicollis. This species comprises two morphs, tan and white, that differ in pigmentation and components of social behavior [3-5]. Morph is determined by alternative alleles at a balanced >100-Mb inversion-based supergene, providing a unique system for studying gene-behavior relationships. Using over two decades of field data, we document near-perfect disassortative mating among morphs, as well as the fitness consequences of rare assortative mating. We use de novo whole-genome sequencing coupled with population- and phylogenomic data to show that alternate supergene alleles are highly divergent at over 1,000 genes and that these alleles originated prior to the split of Z. albicollis from its sister species and may be polymorphic in Z. albicollis due to a past hybridization event. We provide evidence that the "white" allele may be degrading, similar to neo-Y/W sex chromosomes. We further show that the "tan" allele has surprisingly low levels of genetic diversity yet does not show several canonical signatures of recurrent positive selection. We discuss these results in the context of the origin, molecular evolution, and possible fate of this remarkable polymorphism., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Songbirds share some essential traits but are extraordinarily diverse, allowing comparative analyses aimed at identifying specific genotype-phenotype associations. This diversity encompasses traits like vocal communication and complex social behaviors that are of great interest to humans, but that are not well represented in other accessible research organisms. Many songbirds are readily observable in nature and thus afford unique insight into the links between environment and organism. The distinctive organization of the songbird brain will facilitate analysis of genomic links to brain and behavior. Access to the zebra finch genome sequence will, therefore, prompt new questions and provide the ability to answer those questions.