Affiliation:
1. Department of Biology, Boston University5 Cummington Street, Boston, MA 02215, USA
2. Department of Zoology, University of GrazUniversitätsplatz 2, 8010 Graz, Austria
Abstract
Behavioural and molecular studies suggest that brood parasitic indigobirds (Viduaspp.) rapidly diversified through a process of speciation by host shift. However, behavioural imprinting on host song, the key mechanism promoting speciation in this system, may also lead to hybridization and gene flow among established indigobird species when and if female indigobirds parasitize hosts already associated with other indigobird species. It is therefore not clear to what extent the low level of genetic differentiation among indigobird species is due to recent common ancestry versus ongoing gene flow. We tested for reproductive isolation among three indigobird species in Cameroon, one of which comprises two morphologically indistinguishable host races. Mimicry of host songs corresponded with plumage colour in 184 male indigobirds, suggesting that females rarely parasitize the host of another indigobird species. Paternity analyses, however, suggest that imperfect specificity in host and/or mate choice allows for continuing gene flow between recently formed host races of the Cameroon IndigobirdVidua camerunensis; while 63 pairs of close relatives were associated with the same host, two strongly supported father–son pairs included males mimicking the songs of the two different hosts ofV. camerunensis. Thus, complete reproductive isolation is not necessarily an automatic consequence of host shifts, a result that suggests an important role for natural and/or sexual selection in indigobird speciation.
Subject
General Agricultural and Biological Sciences,General Environmental Science,General Immunology and Microbiology,General Biochemistry, Genetics and Molecular Biology,General Medicine
Cited by
18 articles.
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