David Valenzuela-Galván

Living on the edge: roads and edge effects on small mammal populations

1. Roads may affect wildlife populations through habitat loss and disturbances, as they create an abrupt linear edge, increasing the proportion of edge exposed to a different habitat. Three types of edge effects have been recognized: abiotic, direct biotic, and indirect biotic. 2. We explored the direct biotic edge effects of 3- to 4-m wide roads, and also a previously unrecognized type of edge effect: social. We live-trapped two threatened endemic rodents from Cozumel Island (Oryzomys couesi cozumelae and Reithrodontomys spectabilis) in 16 plots delimited by roads on two sides, to compare edge effects between two adjacent edges (corners), single-edge and interior forest, on life history and social variables. 3. No significant edge effects were observed on the life-history variables, with the exception of differences in body condition between males and females of O. c. cozumelae near edges. Both species showed significant and contrasting effects on their social variables. 4. O. c. cozumelae was distributed according to its age and sex: the proportion of adults and males was higher in interior than near edges, while juveniles and females were more abundant near edges. More nonreproductive females were present in corners than in single-edge and interior, while the opposite distribution was observed for nonreproductive males. 5. The distribution of R. spectabilis was related to its age and reproductive condition, but not to its sex. The proportion of adults was significantly higher in corners, while juveniles were only caught in single-edge and interior quadrants. The proportion of reproductive individuals was higher in edge than interior quadrants, while reproductive females were only present in edge quadrants. 6. We found significant differences between the quadrants with the greatest edge exposure in comparison with other quadrants. The social edge effects we identified complement the typology of edge effects recognized in ecological literature. Our study provides insight into the effects that sharp road edges have on biological and social characteristics of small mammal populations, highlighting how such effects vary among species. Our findings have important conservation implications for these threatened species, but are also applicable in a broader context wherever there are abrupt edges caused by linear landscape features.

The Margay Leopardus wiedii and Bobcat Lynx rufus from the Dry Forests of Southern Morelos, Mexico

Abstract During May 2009–June 2010, we obtained five photographs of different margays (Leopardus wiedii) and photographs of two different bobcats (Lynx rufus) in tropical dry forests at Reserva de la Biosfera Sierra de Huautla, Morelos, Mexico. These are the first confirmed records of the margay in Morelos and of the bobcat in the reserve. Records of the margay represent an expansion of its known range in central Mexico. Resumen Entre mayo 2009 y junio 2010, registramos cinco fotos de diferentes margayes (Leopardus wiedii) y dos fotos de diferentes gatos monteses (Lynx rufus) en sitios de selva baja caducifolia en la Reserva de la Biosfera Sierra de Huautla, Morelos, México. Estos registros son la primera evidencia confirmada del margay en Morelos y del gato montés en la reserva. Los registros de margay expanden su rango conocido en el centro de México.

Procyon pygmaeus (Carnivora: Procyonidae)

Abstract Procyon pygmaeus Merriam, 1901, commonly called the Cozumel raccoon, is a procyonid that is endemic to Cozumel Island, Mexico. It is the smallest member of the genus (about 45% lighter and 15–37% smaller in linear measurements than the mainland P. lotor). P. pygmaeus prefers mangrove stands and sandy areas, but it also can be found in semievergreen and subdeciduous tropical forests and agricultural areas. Diet is primarily composed of crabs followed by fruits, insects, crayfish, and small vertebrates. P. pygmaeus is listed as “Critically Endangered” by the International Union for Conservation of Nature and Natural Resources. Introduced congeners and predators, parasite and disease spillover from exotic animals, habitat fragmentation as a result of the expansion and widening of the road system and rapid development of other infrastructure for tourism, and hurricanes are the primary threats to this species.

Transcriptomic analysis of skin pigmentation variation in the Virginia opossum (Didelphis virginiana).

Skin pigmentation and coat pigmentation are two of the best‐studied examples of traits under natural selection given their quantifiable fitness interactions with the environment (e.g., camouflage) and signalling with other organisms (e.g., warning coloration). Previous morphological studies have found that skin pigmentation variation in the Virginia opossum (Didelphis virginiana) is associated with variation in precipitation and temperatures across its distribution range following Glogers rule (lighter pigmentation in temperate environments). To investigate the molecular mechanism associated with skin pigmentation variation, we used RNA‐Seq and quantified gene expression of wild opossums from tropical and temperate populations. Using differential expression analysis and a co‐expression network approach, we found that expression variation in genes with melanocytic and immune functions is significantly associated with the degree of skin pigmentation variation and may be underlying this phenotypic difference. We also found evidence suggesting that the Wnt/β‐catenin signalling pathway might be regulating the depigmentation observed in temperate populations. Based on our study results, we present several alternative hypotheses that may explain Glogers rule pattern of skin pigmentation variation in opossum, including changes in pathogen diversity supporting a pathogen‐resistant hypothesis, thermal stress associated with temperate environments, and pleiotropic and epistatic interactions between melanocytic and immune genes.

Population genomics applications for conservation: the case of the tropical dry forest dweller Peromyscus melanophrys

Recent advances in genomic sequencing have opened new horizons in the study of population genetics and evolution in non-model organisms. However, very few population genomic studies have been performed on wild mammals to understand how the landscape affects the genetic structure of populations, useful information for the conservation of biodiversity. Here, we applied a genomic approach to evaluate the relationship between habitat features and genetic patterns at spatial and temporal scales in an endangered ecosystem, the Tropical Dry Forest (TDF). We studied populations of the Plateau deer mouse Peromyscus melanophrys to analyse its genomic diversity and structure in a TDF protected area in the Huautla Mountain Range (HMR), Mexico based on 8209 SNPs obtained through Genotyping-by-Sequencing. At a spatial scale, we found a significant signature of isolation-by-distance, few significant differences in genetic diversity indices among study sites, and no significant differences between habitats with different levels of human perturbation. At a temporal scale, while genetic diversity levels fluctuated significantly over time, neither seasonality nor disturbance levels had a significant effect. Also, outlier analysis revealed loci potentially under selection. Our results suggest that the population genetics of P. melanophrys may be little impacted by anthropogenic disturbances, or by natural spatial and temporal habitat heterogeneity in our study area. The genome-wide approach adopted here provides data of value for conservation planning, and a baseline to be used as a reference for future studies on the effects of habitat fragmentation and seasonality in the HMR and in TDF.

Velvety Fruit-Eating Bat (Enchistenes hartii; Phyllostomidae) in Morelos, Mexico

Abstract We present here the first record of the velvety fruit-eating bat (Enchistenes hartii; Phyllostomidae) for the state of Morelos, Mexico. Our record gives more insight into the range of the species in Mexico, extending it ca. 52 km into central Mexico, east of the closest reported locality, Malinaltenango, in the state of México. We provide external and cranial measurements of one individual, and information about the habitat where it was captured and other species of bats recorded at the same locality.