Yolanda Hortelano-Moncada

DNA barcodes effectively identify the morphologically similar Common Opossum (Didelphis marsupialis) and Virginia Opossum (Didelphis virginiana) from areas of sympatry in Mexico

Two morphologically similar species of opossum from the genus Didelphis–Didelphis virginiana and Didelphis marsupialis–cooccur sympatrically in Mexico. High intraspecific variation complicates their morphological discrimination, under both field and museum conditions. This study aims to evaluate the utility and reliability of using DNA barcodes (short standardized genome fragments used for DNA-based identification) to distinguish these two species. Sequences of the cytochrome c oxidase subunit I (Cox1) mitochondrial gene were obtained from 12 D. marsupialis and 29 D. virginiana individuals and were compared using the neighbor-joining (NJ) algorithm with Kimuras two-parameter (K2P) model of nucleotide substitution. Average K2P distances were 1.56% within D. virginiana and 1.65% in D. marsupialis. Interspecific distances between D. virginiana and D. marsupialis varied from 7.8 to 9.3% and their barcode sequences formed distinct non-overlapping clusters on NJ trees. All sympatric specimens of both species were effectively discriminated, confirming the utility of Cox1 barcoding as a tool for taxonomic identification of these morphologically similar taxa.

Diversity of Wild Mammals in a Megalopolis: Mexico City, Mexico

Mexico City, the capital of Mexico, is located on the Southern-Central part of the country and it is one of the most important megalopolis in the world. This city lies within the Distrito Federal, bordering with the state of Mexico on the north, east and west and with the state of Morelos on the south. It is one of the 32 political divisions of Mexico and the smallest one, comprising an area of 1,485 km2 (Fig. 1). Mexico City belongs to the Basin of Mexico together with parts of the states of Hidalgo, Puebla, Tlaxcala and Mexico. Mexico City and the rest of the metropolitan area is one of the largest cities in the world with more than 30 million inhabitants (INEGI, 2010), just behind Tokyo, Japan and forward New York and the Philadelphia area, USA (34.3 and 22 respectely; Brinkhoff, 2011). The rapid growth of its population has led to the loss of original habitats and to the transformation of natural sites and therefore and in spite of being considered as a region with high levels of biodiversity to the local extinction of wildlife species. Mammals are one of the most important components of biodiversity, particularly in Mexico. Several inventories and studies have reported the occurrence of mammals in the Valley of Mexico in the past years. Some of the most remarkable contributions to this subject are by far those of Villa-R (1952) and Hall (1981). However, important mammalian information for the Valley of Mexico was also gathered by Ceballos & Galindo (1984) and Villa & Cervantes (2003). Moreover, the paper published by Ramirez-Pulido et al. (1986) more than a quarter of a century ago about mammals of the Distrito Federal contributed important information to the knowledge of the species richness of local mammals species. In addition, several papers reports on mammals collected in diverse areas of the Distrito Federal (Lopez-Forment, 1989; Sanchez et al., 1989; Negrete, 1991; Negrete & Soberon, 1994; Castro-Campillo, 1992; Chavez & Ceballos, 1992, 1994; Chavez, 1993 a, b; Alvarez et al., 1994; Monroy et al., 1999; CONANP-SEMARNAT, 2006; Navarro, et al., 2007; Barcenas & Medellin, 2007; Gomez-Jimenez, 2009). Research papers referriing especially to particular taxonomic groups (Villa-R, 1966; Alvarez & Ramirez-Pulido, 1972; Polaco et al., 2002; Carraway, 2007) also mentioned the presence of mammals in Mexico City and confirmed the outstanding contribution of mammals to the biodiversity of the Distrito Federal. Despite this large number of reports, the available information on mammals of Mexico City was scattered and incomplete. Therefore, in order to properly documents the species

Geographic cranial variation in Peromyscus melanotis (Rodentia: Cricetidae) is related to primary productivity

The black-eared mouse Peromyscus melanotis is distributed in conifer forests and highland prairies throughout the Trans-Mexican Volcanic Belt, Eastern Sierra Madre and Western Sierra Madre in Mexico, and isolated mountain ranges in Arizona, United States. We examined geographic variation in cranial measurements throughout the distribution of the species in Mexico. Because populations of these major ranges are isolated, we expected discontinuities in variation consistent with geographic gaps. Instead, we found no differences between the Sierras and significant differences between them and the Trans-Mexican Volcanic Belt. Moreover, a north-to-south trend of size increase was detected. By relating size to 6 environmental variables, we evaluated 4 hypotheses previously proposed to explain the observed pattern of variation: 1) seasonality, 2) body heat conservation or Bergmanns rule, 3) primary productivity, and 4) body heat dispersion. Significant positive correlations with elevation, productivity, and humidity, and negative correlations with annual mean temperature, temperature seasonality, and latitude led us to conclude that the observed pattern of variation in size is not related to body heat conservation or loss, but driven by primary productivity, a positive correlate of resource availability.