Meeting Abstract
64.1 Tuesday, Jan. 6 Recent sympatric diversification of brood parasitic indigobirds: setting an upper limit on speciation times. DACOSTA, J.M.*; SHULL, H.C.; SEFC, K.M.; BALAKRISHNAN, C.N.; PAYNE, R.B.; SORENSON, M.D.; Boston University; Boston University; Boston University; Boston University; University of Michigan; Boston University dacostaj@bu.edu
Indigobirds (genus Vidua) are host-specific brood parasites in which host colonization and behavioral imprinting have apparently led to sympatric speciation. However, the same behavioral mechanisms that are responsible for speciation in this system can also facilitate introgression among species. Mitochondrial DNA sequences suggest that the four indigobird species in southern Africa evolved after indigobirds from West Africa colonized the region. Given the possibility of ongoing introgression, a possible alternative explanation is that a selectively advantageous West African mtDNA lineage found its way into existing indigobird populations in southern Africa and swept to fixation, thereby obscuring a more ancient origin of the southern species. To test these alternatives, we sequenced several nuclear loci and analyzed these data using coalescent methods designed to simultaneously estimate gene flow and divergence times. Data from nuclear loci were broadly consistent with mtDNA data, indicating recent divergence of western and southern indigobirds as well as relatively low genetic diversity in the south. Coalescent analyses suggest that a small fraction of the ancestral population gave rise to southern indigobirds on the order of 105 years ago, after which there has been little or no gene flow between regions. Thus, four morphologically distinct indigobird species in southern Africa evolved within the region sometime after 105 years ago, consistent with a model of sympatric speciation through host shift.
