MBE Advance Access published online on January 8, 2009
Molecular Biology and Evolution, doi:10.1093/molbev/msp004
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Research Article |
Divergence in the face of gene flow: the case of two newts (Amphibia: Salamandridae)
aw Babik2,3
1 Jagiellonian University, Institute of Environmental Sciences, Gronostajowa 7, 30-387 Kraków, Poland
2 Helmholtz Centre for Environmental Research – UFZ, Department of Community Ecology, Theodor-Lieser-Str. 4, 06120, Halle/Saale, Germany
3 Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Sawkowska 17, 31-016 Kraków, Poland
Corresponding author: Wiesaw Babik, tel. +48 12 422 70 06, fax. +48 12 422 42 94 Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Sawkowska 17, 31-016 Kraków, Poland, email: wieslaw.babik{at}uj.edu.pl
Received for publication October 10, 2008. Revision received January 5, 2009. Accepted for publication January 5, 2009.
Understanding the process of divergence requires the quantitative characterization of patterns of gene flow between diverging taxa. New and powerful coalescent-based methods give insight into these processes in unprecedented details by enabling the reconstruction of the temporal distribution of past gene flow. Here we use sequence variation at eight nuclear markers and mitochondrial DNA (mtDNA) in multiple populations to study diversity, divergence and gene flow between two subspecies of a salamander, the smooth newt (Lissotriton vulgaris kosswigi and L. v. vulgaris) in Turkey. The ranges of both subspecies encompass mainly the areas of this important glacial refugial area. Populations in refugia where species have been present for a long time and differentiated in situ should better preserve the record of past gene flow than young populations in postglacial expansion areas. Sequence diversity in both subspecies was substantial (nuclear 
sil = 0.69 and 1.31%). We detected long-term demographic stability in these refugial populations with large effective population sizes (Ne) of the order of 1.5 - 3 x 105 individuals. Gene trees and the isolation with migration (IM) analysis complemented by tests of nested IM models showed that despite deep, pre-Pleistocene divergence of the studied newts, asymmetric introgression from vulgaris to kosswigi has occurred, with signatures of recent gene flow in mtDNA and an anonymous nuclear marker, and evidence for more ancient introgression in nuclear introns. The distribution of migration times raises the intriguing possibility that even the initial divergence may have occurred in the face of gene flow.
Key Words: Lissotriton vulgaris • divergence • gene flow • nucleotide variation • isolation with migration