Phylogeography of a vanishing North American songbird: The painted bunting (Passerina ciris).

摘要

Studies of genetic variation within and between species can provide insights into their evolutionary history as well as important information for conserving biodiversity. An understanding of population processes can assist in the conservation of biodiversity by contrasting current versus historical patterns, and the processes that have generated these patterns. Genetic differentiation often coincides with significant geological or climatic changes that have shaped the sizes and locations of the species geographic range and altered the connectivity between populations over time. Phylogenetic and population genetic analyses can also provide a statistical framework for the investigation of how human processes such as habitat loss, population connectivity, overexploitation, and species introductions can affect biodiversity.;Here, I employ a suite of phylogenetic and population genetic analyses to address several questions regarding the phylogenetic relationships of the Nearctic-Neotropical migratory songbird: the Painted Bunting (Passerina ciris). The Painted Bunting breeds in the southeast and south central United States and winters in the Florida Keys, the Caribbean, Mexico and portions of Central America. The Atlantic Coast population of the Painted Bunting is a bird of considerable conservation concern. The biotic history of this part of North America has been examined using a wide variety of vertebrates. Many species have had their geographic ranges shift repeatedly during Pleistocene glaciations and many geographic features have been suggested as possible barriers to gene flow.;I begin by reconstructing the phylogeny of the genus Passerina and three members of the closely related genus Cyanocompsa to address issues concerning the evolution of migration within the Passerina clade and the role, geographical source, and timing of range expansions within the Painted Bunting. Data presented herein support the hypotheses that the Painted Bunting split from its sister, the Varied Bunting approximately 1.5--2.1 million years ago during the Pleistocene and that the evolution of migration within the bunting phylogeny evolved independently two times. Additionally, the Painted Bunting is embedded within an otherwise sedentary clade of Mexican birds indicating that the Painted Buntings ancestor is of Mexican origin. Genetic analyses of populations within the breeding grounds indicate that the allopatric Painted Bunting populations diverged approximately 26,000--115,000 years ago and represent incipient species and as such the Atlantic Coast and interior populations should be recognized as separate management units. Hypotheses concerning the patterns of connection between the breeding and overwintering ranges also suggest a general separation between the Atlantic Coast breeding and Caribbean wintering areas from the interior breeding and Mexican/Central American wintering grounds.