Alaska Science Center
A climate for speciation: Rapid spatial diversification among the Sorex cinereus complex of shrews
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Full Publication: http://dx.doi.org/10.1016/j.ympev.2012.05.021
Product Type: Journal Article
The cyclic climate regime of the late Quaternary caused dramatic environmental change at high latitudes. Although these events may have been brief in periodicity from an evolutionary standpoint, multiple episodes of allopatry and divergence have been implicated in rapid radiations of a number of organisms. Shrews of the Sorex cinereuscomplex have long challenged taxonomists due to similar morphology and often-contiguous geographic ranges. Here, multi-locus phylogenetic and demographic assessments using a coalescent framework were combined to investigate spatiotemporal evolution of 13 nominal species with a widespread distribution throughout North America and across Beringia into Siberia. For these species, we first test a hypothesis of recent differentiation in response to Pleistocene climate versus more ancient divergence that would coincide with pre-Pleistocene perturbations. We then investigate the processes driving diversification over multiple continents. Our genetic analyses highlight novel diversity within these morphologically conserved mammals, helping to clarify relationships between geographic distribution and evolutionary history. Demography within and among species indicates both regional stability and rapid expansion. Ancestral ecological differentiation coincident with early cladogenesis within the complex enabled a diversification ratchet where successive glacial and interglacial phases alternately promoted divergence. The cinereus complex constitutes a valuable model for future comparative assessments of evolution in response to cyclic environmental change.