Multiple refugia and barriers explain the phylogeography of the Valais shrew, Sorex antinorii (Mammalia: Soricomorpha)[2012] (original) (raw)

The aim of the present study was to investigate the genetic structure of the Valais shrew (Sorex antinorii) by a combined phylogeographical and landscape genetic approach, and thereby to infer the locations of glacial refugia and establish the influence of geographical barriers. We sequenced part of the mitochondrial cytochrome b (cyt b) gene of 179 individuals of S. antinorii sampled across the entire species' range. Six specimens attributed to S. arunchi were included in the analysis. The phylogeographical pattern was assessed by Bayesian molecular phylogenetic reconstruction, population genetic analyses, and a species distribution modelling (SDM)-based hindcasting approach. We also used landscape genetics (including isolation-by-resistance) to infer the determinants of current intra-specific genetic structure. The phylogeographical analysis revealed shallow divergence among haplotypes and no clear substructure within S. antinorii. The starlike structure of the median-joining network is consistent with population expansion from a single refugium, probably located in the Apennines. Long branches observed on the same network also suggest that another refugium may have existed in the north-eastern part of Italy. This result is consistent with SDM, which also suggests several habitable areas for S. antinorii in the Italian peninsula during the LGM. Therefore S. antinorii appears to have occupied disconnected glacial refugia in the Italian peninsula, supporting previous data for other species showing multiple refugia within southern refugial areas. By coupling genetic analyses and SDM, we were able to infer how past climatic suitability contributed to genetic divergence of populations. The genetic differentiation shown in the present study does not support the specific status of S. arunchi. P. 2006. Hares on thin ice: introgression of mitochondrial DNA in hares and its implications for recent phylogenetic analyses. Molecular Phylogenetics and Evolution 40: 640-641. Araújo MB, New M. 2007. Ensemble forecasting of species distributions. Trends in Ecology and Evolution 22: 42-47. Avise J. 2000. Phylogeography: the history and formation of species. Cambridge, MA: Harvard University Press. Bandelt H-J, Forster P, Röhl A. 1999. Median-joining networks for inferring intraspecific phylogenies. Molecular Biology and Evolution 16: 37-48. Basset P, Yannic G, Hausser J. 2006. Genetic and karyotypic structure in the shrews of the Sorex araneus group: are they independent? Molecular Ecology 15: 1577-1587. Bilton DT, Mirol PM, Mascheretti S, Fredga K, Zima J, Searle JB. 1998. Mediterranean Europe as an area of endemism for small mammals rather than a source for northwards postglacial colonization. Proceedings of the Royal Society of London Series B, Biological Sciences 265: 1219-1226. Brünner H, Lugon-Moulin N, Balloux F, Fumagalli L, Hausser J. 2002. A taxonomical re-evaluation of the Valais chromosome race of the common shrew Sorex araneus (Insectivora: Soricidae). Acta Theriologica 47: 245-275. Canestrelli D, Cimmaruta R, Nascetti G. 2007. Phylogeography and historical demography of the Italian treefrog, Hyla intermedia, reveals multiple refugia, population expansions and secondary contacts within peninsular Italy. Molecular Ecology 16: 4808-4482. Canestrelli D, Cimmaruta R, Nascetti G. 2008. Population genetic structure and diversity of the Apennine endemic stream frog, Rana italica -insights on the Pleistocene evolutionary history of the Italian peninsular biota. Molecular Ecology 17: 3856-3872.