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We investigated the biogeographic history of antelope squirrels, genus Ammospermophilus, which are widely distributed across the deserts and other arid lands of western North America. We combined range-wide sampling of all currently recognized species of Ammospermophilus with a multilocus data set to infer phylogenetic relationships. We then estimated divergence times within identified clades of Ammospermophilus using fossil-calibrated and rate-calibrated molecular clocks. Lastly, we explored generalized distributional changes of Ammospermophilus since the last glacial maximum using species distribution models, and assessed responses to Quaternary climate change by generating demographic parameter estimates for the three wide-ranging clades of A. leucurus. From our phylogenetic estimates we inferred strong phylogeographic structure within Ammospermophilus and the presence of three well-supported major clades. Initial patterns of historical divergence were coincident with dynamic alterations in the landscape of western North America, and the formation of regional deserts during the Late Miocene and Pliocene. Species distribution models and demographic parameter estimates revealed patterns of recent population expansion in response to glacial retreat. When combined with evidence from co-distributed taxa, the historical biogeography of Ammospermophilus provides additional insight into the mechanisms that impacted diversification of arid-adapted taxa across the arid lands of western North America. We propose species recognition of populations of the southern Baja California peninsula to best represent our current understanding of evolutionary relationships among genetic units of Ammospermophilus. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109, 949-967. [ABSTRACT FROM AUTHOR]

Thomomys atrovarius is redescribed to include the smooth-toothed pocket gophers that inhabit dry, thornscrub vegetation along the Pacific versant of the Sierra Madre Occidental of Mexico from northern Sinaloa into western Durango, northwestern Jalisco, and western Nayarit. Molecular analyses of mitochondrial and nuclear DNA sequences (including historical samples from museum skins) show high levels of genetic differentiation between T. atrovarius and T. umbrinus of the Sierra Madre Occidental (15.4% cytochrome-b divergence) and Mexican Central Plateau (16.9% divergence). Roughly coincident morphometric and genetic gaps divide T. atrovarius into 2 subspecies, T. a. parviceps in the north and T. a. atrovarius in the south, with probable intergradation in between. Most specimens of T. atrovarius, especially those of the southern subspecies, are distinguished easily from specimens of T. bottae and T. umbrinus on the basis of fur texture, and an analysis of cranial morphometrics shows little overlap between T. atrovarius and other Thomomys clades in Mexico. An analysis of niche parameters shows significantly different climate envelopes for T. atrovarius compared with other species of Thomomys, and a biogeographical review suggests that T. atrovarius has ancestral affinities to the south of its current distribution. A synonymy of T. atrovarius and a key to the currently recognized species of Thomomys in mainland Mexico are provided. [ABSTRACT FROM AUTHOR]

We review the expanding role of molecular genetics in the emergence of a vibrant and vital integrative biogeography. The enormous growth over the past several decades in the number and variety of molecular-based phylogenetic and population genetics studies has become the core information used by biogeographers to reconstruct the causal connections between historical evolutionary and ecological attributes of taxa and biotas, and the landscapes and seascapes that contain them. A proliferation of different approaches, sequences, and genomes have provided for the integration of a 'biogeography of the Late Neogene' with other Earth and biological sciences under the rubrics of phylogeography, landscape genetics, and phylochronology. Approaches designed explicitly to take advantage of unique properties of molecular genetic information have led to the re-emergence of dispersal as an analytically tractable process that historical biogeographers can now use, along with vicariance, to reconstruct the geographical context of diversification. Concomitant with the expanding amount of information available, molecular data sets often provide for estimates of lineage divergence dates, and analytical tools for doing so continue to improve. The comparability of molecular-based estimates of phylogenetic and population genetic histories across non-related taxa has stimulated deployment of new methods to test for spatial and temporal congruence across co-distributed taxa and ecosystems, and thus increased rigour in hypothesis-testing. We illustrate how a molecular genetics framework has provided robust and novel reconstructions of historical biogeographical pattern and process in three different systems, and finish with some thoughts on the role a molecular genetic-based biogeography will play in predicting alternative futures of biodiversity. [ABSTRACT FROM AUTHOR]