Phylogeography of the Northern short‐tailed shrew, Blarina brevicauda (Insectivora: Soricidae): past fragmentation and postglacial recolonization

Abstract

Blarina brevicauda is distributed across the northeastern region of North America, in areas previously covered by Pleistocene glaciers. Previous molecular systematic study of the species in the genus Blarina suggested the presence of two distinct eastern and western phylogroups within B. brevicauda, in agreement with traditionally recognized semi-species. To expand the previous work, a collection of 76 individuals from 14 localities collected throughout the range of B. brevicauda was used to assess the mitochondrial (mt) cytochrome b genealogy for this species. Minimum evolution, maximum parsimony, analysis of molecular variance and nested clade analysis each supported the same conclusions of two well-differentiated and monophyletic east-west groups, separated by the Mississippi River. Denser sampling in areas immediately East of the Mississippi basin revealed further subdivision within the eastern phylogroup into an East-Central and an Appalachian clade. The western phylogroup differed from the eastern phylogroup by 2.5% mean absolute DNA sequence difference. About 65% of the genetic variance among samples was explained by the east-west subdivision alone. High haplotype diversities, low nucleotide diversities and unimodal mismatch distributions within subclades suggest recent expansion or diversification within each group. No phylogeographic structure was found within the western phylogroup, but genetic structure because of restricted gene flow and isolation by distance was inferred for the eastern group. The present distribution of B. brevicauda is best explained by past fragmentation and range expansion events during and following the Pleistocene glacial cycles.

Phylogenetic relationship betweenCallosciurus canicepsandC. inornatus(Rodentia, Sciuridae): Implications for zoogeographical isolation by the Mekong River

“…For instance, populations of red fox, Vulpes vulpes (Linnaeus, 1758) isolated by the Mississippi River in Iowa and Illinois have different skull morphologies (Storm et al 1976). The Mississippi River also genetically separates east and west groups of shorttailed shrew, Blarina brevicauda (Say, 1823) (Brant & Orti 2003). The role of rivers in forming genetic diversity has been especially important for arboreal primates.…”

Predicting Pleistocene climate from vegetation in North America

“…Genetic data for red maple further support refugia close to the ice (Soltis et al, 2006). Evidence is also accumulating for southern Appalachian refugia for various animal species (e.g., Austin et al, 2002Austin et al, , 2004Brant and Ortí, 2003;Church et al, 2003). The genetics data for Liriodendron point to a number of distinct races.…”

A striking lack of genetic diversity across the wide-ranging amphibian Gastrophryne carolinensis (Anura: Microhylidae)

“…For anurans, many species with broad geographic ranges concordant with G. carolinenisis in the eastern U.S. are comprised of cryptic genetic lineages (Table 4). In addition, the general finding of phylogeographic structure across populations of a single species is also common in reptiles (Rodriguez-Robles et al 1999;Burbrink et al 2000;Janzen et al 2002;Starkey et al 2003;Kasapidis et al 2005;Howes et al 2006;Castoe et al 2007), mammals (Brant and Orti 2003;Dragoo et al 2006), birds (Nittinger et al 2007), insects (Downie 2004), and fish (Strange and Burr 1997;Berendzen et al 2003). More broadly, Swenson and Howard (2004) provided a comprehensive survey of all known phylogeographic breaks, hybrid zones, and contact zones…”