Speciation in Brood Parasitic Indigobirds

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Sorenson0089757The African indigobirds (genus Vidua) are obligate brood parasites, reproducing only by laying their eggs in the nests of other species. Indigobirds are highly host-specific and the young parasites precisely mimic the mouth colors and patterns in the young of their respective hosts. As adults, male indigobirds mimic the songs of their hosts. This behavior results in the genetic cohesion of indigobird species because females also imprint on the host species and choose their mates based on song. These same behavioral mechanisms, however, may result in reproductive isolation and rapid speciation after the colonization of a new host species. This research will use molecular genetic markers to investigate the evolutionary history and genetic structure of indigobird species and populations using samples from over 500 indigobirds collected throughout Africa. In addition, an intensive field study in Cameroon will directly evaluate the incidence of ongoing hybridization and genetic introgression among indigobird populations using different hosts.The indigobird system is a remarkable example of rapid evolutionary diversification and adaptive evolution and represents one of those unusual situations in which the evolutionary process can be studied in progress. This research will contribute to a renewed interest among evolutionary biologists in the mechanisms of speciation and the roles of natural and sexual selection in generating biodiversity. A clear understanding of the evolutionary history and genetic structure of indigobird populations will also lay the groundwork for future analyses of the genetic and developmental mechanisms underlying mouth mimicry, the key genetic adaptation of these host-specific brood parasites.