Gene-Culture interactions in the evolution of birdsong

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Bengalese finches are domesticated strain of the white-romped munia. The process of domestication dates back some 240 years when wild white-rumped munias were imported to Japan from South China. Although the wild strain sings simple linear song for mate attraction, the domesticated strain sings complex songs that could be expressed by finite-state automata. We hypothesized that domestication relaxed some of the selection pressures including foraging and predation costs and sexual selection remained as a main selection pressure for song. Thus cultural and genetic factors should differentiate the songs between the two strains. We performed field and laboratory works to prove some of these hypotheses.Lesioning a part of song control nuclei in Bengalese finches resulted in simplification of the song, suggesting that there should be some brain mechanisms that account for the differences in songs. To ask the degree of innateness in song learning, we cross-fostered chicks of white-rumped munias and Bengalese finches. Some of rapid frequency modulations and complex syntax structures were not learned by the cross-fostered white-rumped munias, suggesting the existence of innate bias for song learning.To detect genes responsible for the innate bias for song learning, we developed a 5,000-clone cDNA microarray and found some candidate genes. Based on the array analyses, we performed in-situ hybridization studies to identify brain distribution of these genes. Differences were found in a sub-type of the NMDA receptor in basal ganglia and a sub-type of the PKC in arcopallium. Although functional contribution of these genes in songs of the two strains, we began to understand the cultural influence of genetic compositions. Through these researches we hope to clarify the mechanisms of gene-culture co-evolution in behavior.