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Phylogeography of the California Gnatcatcher (Polioptila californica) using multilocus DNA sequences and ecological niche modeling - Filogeografía de Polioptila californica basada en Secuencias de ADN Multilocus y Modelamiento de Nicho Ecológico: Implications for conservation
Robert M. Zink, Jeffrey G. Groth, Hernan Vázquez-Miranda and George F. Barrowclough
Vol. 130, No. 3 (July 2013), pp. 449-458
Published by: American Ornithologists' Union
Stable URL: http://www.jstor.org/stable/10.1525/auk.2013.12241
Page Count: 10
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Abstract An important step in conservation is to identify whether threatened populations are evolutionarily discrete and significant to the species. A prior mitochondrial DNA (mtDNA) phylogeographic study of the California Gnatcatcher (Polioptila californica) revealed no geographic structure and, thus, did not support the subspecies validity of the threatened coastal California Gnatcatcher (P. c. californica). The U.S. Fish and Wildlife Service concluded that mtDNA data alone were insufficient to test subspecies taxonomy. We sequenced eight nuclear loci to search for historically discrete groupings that might have been missed by the mtDNA study (which we confirmed with new ND2 sequences). Phylogenetic analyses of the nuclear loci revealed no historically significant groupings and a low level of divergence (GST = 0.013). Sequence data suggested an older population increase in southern populations, consistent with niche modeling that suggested a northward range expansion following the Last Glacial Maximum (LGM). The signal of population increase was most evident in the mtDNA data, revealing the importance of including loci with short coalescence times. The threatened subspecies inhabits the distinctive Coastal Sage Scrub ecosystem, which might indicate ecological differentiation, but a test of niche divergence was insignificant. The best available genetic, morphological, and ecological data indicate a southward population displacement during the LGM followed by northward range expansion, without the occurrence of significant isolating barriers having led to the existence of evolutionarily discrete subspecies or distinct population segments that would qualify as listable units under the Endangered Species Act.
© 2013 by The American Ornithologists' Union