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Three species of Mexican deer mice of the Peromyscus mexicanus species group (P. grandis, P. guatemalensis, and P. mrhynchus) 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 individuais 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. DOI: 10.1644/09-MAMM-A-167.1. Key words: cytochrome b, morphometrics, Peromyscus, Peromyscus mexicanus species group

As presently recognized, the genus Galea is composed of 3 species, G. musteloides, G. flavidens, and G. spixii. The most widely distributed species is G. musteloides (the common yellow-toothed cavy), ranging from southern Pena to southern Argentina and from sea level to over 4,000 m elevation. Our current taxonomic and systematic understanding of Galea is based primarily on morphological studies that have been limited in both taxonomic and geographic sampling. In this study phylogenetic analyses of sequences from the cytochrome-b gene were used to test hypotheses related to the content, limits, and systematic relationships within G. musteloides. Our data support restricting G. musteloides to the highlands of northwestern Bolivia, southeastern Pena, and extreme northeastern Chile. We elevate G. leucoblephara Burmeister, 1861, for populations occupying the lowlands of Bolivia and Paraguay to central Argentina, and we elevate G. comes Thomas, 1919, for populations from the Andes of southern Bolivia and northern Argentina. Our results also suggest the presence of a previously unrecognized form at midelevations in the southern Bolivian Andes. We find support for treating G. spixii campicola as a junior synonym of G. l. demissa and G. monasteriensis as a junior synonym of G. musteloides boliviensis. Most of the evolution of the taxa within the G. musteloides complex appears to have occurred in the Prepuna biogeographic province, with 2 independent vicariant events culminating in the separation of the G. musteloides, G. comes, and G. leucoblephara clades. Dating estimates suggest a late Miocene divergence between G. spixii and the G. musteloides group, followed by species-level divergence within the G. musteloides group during the Pliocene. DOI: 10.1644/08-MAMM-A-214R1.1. Key words: BEAST, Caviomorpha, cytochrome b, Hystricognathi, phylogenetics, South America [c] 2010 American Society of Mammalogists

We present the most comprehensive systematic study to date of Necromys, a rodent genus distributed in open areas north and south of Amazonia and in Andean grasslands. The study is based on sequences of the cytochrome-b gene that were analyzed by parsimony and Bayesian approaches. The analyses include sequences of 62 specimens from 51 localities from Argentina, Bolivia, Brazil, Colombia, Paraguay, Peru, Uruguay, and Venezuela, representing all but 1 of the species currently recognized in the genus. Necromys was recovered as a monophyletic group and we found a large polytomy at its base that involves 3 lineages. One, represented by the Andean N. lactens, shows a marked phylogeographic pattern. The 2nd clade is formed by N. urichi from the northern grasslands of South America and N. amoenus from the central Andes. Results suggest that each of these taxa may represent more than 1 biological species. The 3rd clade is formed by lowland species found south of Amazonia. Within this clade N. obscurus is sister to the remaining species. Haplotypes recovered from specimens assigned to N. benefactus, N. temchuki, and N. lasiurus form a clade, but these taxa do not form reciprocally monophyletic groups, nor does this large clade possess geographic structure. These genealogical results, discussed in the context of genetic variation, are the basis of taxonomic (e.g., N. benefactus and N. temchuki are regarded as junior synonyms of N. lasiurus) and biogeographic considerations. Key words: Bolomys, Cabreramys, Cricetidae, gene tree, Muroidea, Necromys, South America, systematics, taxonomy, Zygodontomys

We predicted that more-fragmented habitats are associated with lower diversity of small mammals and higher densities of populations of rodents that are hosts of hantaviruses. We compared diversity and distribution of small mammals that are either hosts or nonhosts of hantaviruses in 6 Panamanian national parks and adjacent areas with varying degree of human impacts. We sampled forest, edge, and anthropogenically disturbed habitats. The generalist rodents Oligoryzomys fidvescens (reservoir of Choclo virus) and Zygodontomys brevicauda (reservoir of Calabazo virus) were more abundant in disturbed habitats, especially in smaller and more isolated patches, where population density and diversity of other rodent species was lowest. In contrast, these 2 species had lower abundances in larger forested areas with more nonreservoir species of small mammals. Our results suggest that the change in the natural environment resulting from tropical deforestation is increasing the abundance and distribution of species that are reservoirs for hantaviruses. Therefore, it is likely that forest fragmentation has contributed to recent outbreaks of hantavirus pulmonary syndrome in tropical areas. Conservation of natural resources becomes all the more imperative, not only for protecting fauna and flora but also for human health. Key words: diversity loss, emerging diseases, generalist rodents, habitat fragmentation, hantavirus reservoirs, Panama

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