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Aim: Quantitatively evaluate the similarity of genomic variation and geography in five different alpine small mammals in Alaska, and use this quantitative assessment of concordance as a framework for refining hypotheses about the processes structuring population genetic variation in either a species-specific or shared manner. Location: Alaska and adjacent north-western Canada. Methods: For each taxon we generated 3500-7500 single-nucleotide polymorphisms and applied a Procrustes analysis to find an optimal transformation that maximizes the similarity between principal components analysis maps of genetic variation and geographical maps of sample locations. We generate stability maps using projected distributions from ecological niche models of the Last Glacial Maximum and the present. Results: Significant similarity between genes and geography exists across taxa. However, the extent to which geography is predictive of patterns of genetic variation not only differs among taxa, but the correspondence between genes and geography varies over space. Geographical areas where genetic structure aligns poorly with the geographical coordinates are of particular interest because they indicate regions where processes other than isolation by distance (IBD) have influenced genetic variation. The clustering of individuals according to their sample location does not support suppositions of admixture, despite the presumed high vagility of some species (e.g. arctic ground squirrels). Main conclusions: Genomic data indicate a more nuanced biogeographical history for the taxa than suggested by previous studies based on mtDNA alone. These include departures from IBD that are shared among taxa, which suggest some shared processes structuring genetic variation, including new potential ancestral source populations. In addition, some regions fit expectations of IBD where incremental migration and gene flow play a strong role in population structure, despite any ecological difference among taxa. Differences in dispersal capabilities do not result in different species-specific local patterns of population structure, at least at the sampling scale examined here. We highlight how the general fit to, as well as departures from, expectations for patterns of genetic variation based on the Procrustes analyses can be used to generate hypotheses about the underlying processes. [ABSTRACT FROM AUTHOR]

Identifying the genetic structure of a species and the factors that drive it is an important first step in modern population management, in part because populations evolving from separate ancestral sources may possess potentially different characteristics. This is especially true for climate-sensitive species such as pikas, where the delimitation of distinct genetic units and the characterization of population responses to contemporary and historical environmental pressures are of particular interest. We combined a restriction site-associated DNA sequencing ( RADSeq) data set containing 4156 single nucleotide polymorphisms with ecological niche models ( ENMs) of present and past habitat suitability to characterize population composition and evaluate the effects of historical range shifts, contemporary climates and landscape factors on gene flow in Collared Pikas, which are found in Alaska and adjacent regions of northwestern Canada and are the lesser-studied of North America's two pika species. The results suggest that contemporary environmental factors contribute little to current population connectivity. Instead, genetic diversity is strongly shaped by the presence of three ancestral lineages isolated during the Pleistocene (~148 and 52 kya). Based on ENMs and genetic data, populations originating from a northern refugium experienced longer-term stability, whereas both southern lineages underwent population expansion - contradicting the southern stability and northern expansion patterns seen in many other taxa. Current populations are comparable with respect to generally low diversity within populations and little-to-no recent admixture. The predominance of divergent histories structuring populations implies that if we are to understand and manage pika populations, we must specifically assess and accurately account for the forces underlying genetic similarity. [ABSTRACT FROM AUTHOR]

Aim  Pleistocene climatic cycles have left marked signatures in the spatial and historical genetic structure of high-latitude organisms. We examine the mitochondrial (cytochrome b) genetic structure of the singing vole, Microtus miurus (Rodentia: Cricetidae: Arvicolinae), a member of the Pleistocene Beringian fauna, and of the insular vole, Microtus abbreviatus, its putative sister species found only on the St Matthew Archipelago. We reconstruct the phylogenetic and phylogeographical structure of these taxa, characterize their geographical partitioning and date coalescent and cladogenetic events in these species. Finally, we compare the recovered results with the phylogenetic, coalescent and spatial genetic patterns of other eastern Beringian mammals and high-latitude arvicoline rodents. Location  Continental Alaska (alpine and arctic tundra) and the St Matthew Archipelago (Bering Sea). Methods  We generated and analysed cytochrome b sequences of 97 singing and insular voles ( M. miurus and M. abbreviatus) from Alaska. Deep evolutionary structure was inferred by phylogenetic analysis using parsimony, maximum likelihood and Bayesian approaches; the geographical structure of genetic diversity was assessed using analysis of molecular variance and network analysis; ages of cladogenetic and coalescent events were estimated using a relaxed molecular clock model with Bayesian approximation. Results  Regional nucleotide diversity in singing voles is higher than in other high-latitude arvicoline species, but intra-population diversity is within the observed range of values for arvicolines. Microtus abbreviatus specimens are phylogenetically nested within M. miurus. Molecular divergence date estimates indicate that current genetic diversity was formed in the last glacial (Wisconsinan) and previous interglacial (Sangamonian) periods, with the exception of a Middle Pleistocene split found between samples collected in the Wrangell Mountains region and all other singing vole samples. Main conclusions  High levels of phylogenetic and spatial structure are observed among analysed populations. This pattern is consistent with that expected for a taxon with a long history in Beringia. The spatial genetic structure of continental singing voles differs in its northern and southern ranges, possibly reflecting differences in habitat distribution between arctic and alpine tundra. Our phylogenetic results support the taxonomic inclusion of M. miurus in its senior synonym, M. abbreviatus. [ABSTRACT FROM AUTHOR]