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Phylogeographic relationships were evaluated at the intraspecific level using nucleotide sequence data from the mitochondrial cytochrome b gene of representative specimens of 'colilargo' (Oligoryzomys longicaudatus) from 31 localities, along its distributional range over a large part of the western Andes and southern Argentina. Based on approximately 1,000 base pairs (bp), we recognized a single species on both the Chilean and the Argentinean side as far as at least latitude 51[degrees]S, rejecting the subspecific distinctiveness of longicaudatus and philippi. We thus placed the latter in full synonymy with O. longicaudatus as earlier studies proposed, and enlarged its range as far as Torres del Paine, about 51[degrees]S. The occurrence of subspecies in this range is doubtful given the low sequence divergence values and the absence of significant associations between haplotypes and their geography. Additionally, we hypothesized that the entrance of this species into the Chilean side of the Andes mountains occurred through the Patagonian forests of southern Argentina, with further dispersal to the north from the south. Key words: Argentina, Chile, cytochrome b gene, Oligocyzomys longicaudatus, phylogeography

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Phylogenetic analyses were conducted on cytochrome b sequence data of the most geographically and taxonomically broad sampling of Cavia taxa to date. Primary objectives included providing the first extensive molecular phylogenetic framework for the genus, testing the taxonomic and systematic hypotheses of previous authors and providing insight into the evolutionary and biogeographic history of the genus. Support was found for the morphologically defined species C. aperea, C. tschudii, C. magna and C. fulgida and the taxonomic placement of taxa previously subject to conflicting taxonomic opinions (e.g. C. nana, C. anolaimae and C. guianae) was further resolved. Additionally, we elevate the Ecuadorian C. a. patzelti to species status, restrict the distributional limits and suggest taxonomic affiliations of some C. tschudii subspecies, and provide strong evidence for the geographic origin of guinea pig domestication. Finally, we provide an estimated evolutionary timeline for the genus Cavia, which appears to extend well into the late Miocene. [ABSTRACT FROM AUTHOR]

Sequences from two mitochondrial genes (cytochrome b and NADH1) were used to produce a molecular phylogeny for 12 named and two undescribed species of the genus Oligoryzomys. All analyses placed Oligoryzomys microtis as the most basal taxon, a finding consistent with previous studies that suggested the west-central Amazon as a centre of origin for the tribe Oryzomyini to which Oligoryzomys belongs. Biogeographically, this suggests that Oligoryzomys had a South American origin, and later advanced northwards, entering Central America and Mexico more recently. Different analyses have provided consistent support for several additional clades that did not necessarily agree with the species groups hypothesized by previous studies. A molecular clock derived for these data suggests an origin for the genus of 6.67 Mya, with most speciation within the genus occurring between 3.7 and 1.5 Mya. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, , 551-566. [ABSTRACT FROM AUTHOR]

Three species of Mexican deer mice of the Peromyscus mexicanus species group (P. grandis, P. guatemalensis, and P. zarhynchus) were characterized morphologically and genetically to test hypothesized concepts of species limits. We investigated if previously proposed phenetic relationships among these 3 taxa were supported by morphometric and genetic data. Analyses of nongeographic and geographic variation for individuals from 36 localities in Guatemala and southeastern Mexico were conducted to assay morphologic and geographic boundaries. In addition, 35 mitochondrial cytochrome-b gene sequences were analyzed using maximum-parsimony and Bayesian inference methods to determine relationships among the 3 taxa. This study based on comparisons to type specimens provided support for the presence of 3 morphologically and genetically distinct units. Our analyses suggest that P. grandis and P. guatemalensis are more closely related to each other than either is to P. zarhynchus, rejecting existing hypotheses that suggest that P. zarhynchus and P. grandis are phenetically more similar. The results of this study depict relationships among other members of the P. mexicanus group and patterns of speciation and biogeography and allow identification of regionally important phylogeographic units in Mesoamerica. [ABSTRACT FROM AUTHOR]