Evelyn Rios

Revision of the Dipodomys Merriami Complex in the Baja California Peninsula, Mexico

Abstract The kangaroo rat Dipodomys merriami occurs widely over the Baja California peninsula, inhabiting all the arid and sandy lowlands. Its range encompasses diverse climatic, edaphic, and vegetation zones, including 2 islands. The 11 taxa recognized in the merriami complex in this region almost 50 years ago remain valid to the present. The 2 island forms originally were described as different species, and have been treated in different ways by subsequent authors. In this investigation we used a genetic analysis of 2 mitochondrial genes, cytochrome b (Cytb) and cytochrome c oxidase subunit III (COIII), to study patterns of genetic structuring in this species throughout the peninsula. We supplemented existing morphometric and pelage color data with new data, and integrated these data sets into a phylogenetic analysis. Finally, we explored how our results compared with the existing taxonomic arrangement of species and subspecies. Our phylogenetic analyses of molecular data used the concatenation of 1,140 base pairs (bp) of the Cytb gene and 690 bp of the COIII gene; cladograms were generated using maximum-parsimony, maximum-likelihood, and Bayesian inference procedures. A hierarchy of nested clades was produced, the highest level of which revealed 2 reciprocally monophyletic clades separated by 20 mutational steps. There is a Southern Clade extending north to the Vizcaíno Desert in the west and San José Island in the east, and a Northern Clade that includes all the populations farther to the north. At a shallower level, the Southern Clade contains 4 subclades, including the populations of San José and Margarita islands, whereas the Northern Clade is composed of 3 subclades. Adding the morphometric and pelage coloration data sets to the analyses resulted in support for the 11 previously recognized taxa arranged in a single species, Dipodomys merriami, but with improved understanding of how the subspecies relate to each other. As is increasingly appreciated, our investigation supports a comprehensive approach involving multiple data sets that are sensitive to a wide temporal range of evolutionary history for phylogenetic reconstruction.

Phylogeography and systematics of the San Diego pocket mouse (Chaetodipus fallax)

Abstract The systematics and phylogeography of the San Diego pocket mouse (Chaetodipus fallax), a species restricted to the Baja California Peninsula and adjacent southwestern California, were assessed using sequences of the mitochondrial cytochrome-b gene (Cytb). Genetic relationships were evaluated among the 6 recognized subspecies of C. fallax (including the island population, C. f. anthonyi) in 3 geographic regions from individuals representing 22 populations. Analysis of molecular variance and multiple phylogenetic analyses indicated 3 main clades: northern populations in the southwestern Mojave Desert and Los Angeles Basin north of the Salton Trough; central populations from south of the Salton Trough and throughout the state of Baja California; and southern populations from west of the Vizcaíno Desert in Baja California Sur and adjacent Isla Cedros. These clades do not correspond to the currently recognized subspecies, and each could be considered a distinct subspecies pending analysis of nuclear DNA or characters (e.g., morphology) encoded by nuclear DNA.

DNA Barcoding of Mammals in Mexico: Implications for Biodiversity

The Mexican Barcode of Life (MEXBOL) project started as an initiative by researchers who wanted Mexico to join the international DNA barcoding (iBOL) collaboration to establish a genetic system of species identification and discovery. MEXBOL has three main nodes associated with different research institutions in the northern, central, and southern parts of the country. At the beginning of 2009, the laboratories of the three nodes began to operate with support from the University of Guelph in Canada where DNA barcoding began in 2003. By the end of 2011, the laboratories in Mexico will be completely equipped and fully operational. The project is funded by the Consejo Nacional de Ciencia y Tecnologia (CONACyT). In addition, the steering committee of MEXBOL supports the Comision Nacional para el Conocimiento y Uso de la Biodiversidad (CONABIO) initiative to offer grants to any university and research center for barcoding collections of Mexican specimens. We present preliminary results of projects dealing with barcoding Mexican mammals. The aims of these analyses are to evaluate the importance of the DNA barcoding (using cytochrome c oxidase subunit I gene; COI) for the identification of species, study of genetic diversity, and taxonomic review. Our preliminary data suggest that DNA barcodes can be used for the discovery of cryptic species and have important implications to the understanding of the mega-diversity of mammals in Mexico.

Genetic variation in Heteromys nelsoni (Rodentia: Heteromyidae) reveals its possible natural extinction

Abstract Heteromys nelsoni is restricted to cloud forests in the mountain range of the southern state of Chiapas, Mexico, and western Guatemala. It is considered an endemic species, under special protection, and endangered because its habitat has been modified by excessive logging and extensive cattle grazing. We evaluated the genetic variation of H. nelsoni and the relationship between individuals from two geographic areas surrounding Cerro Mozotal, Chiapas, using three mitochondrial genes [cytochrome b (Cyt b), cytochrome c oxidase subunit 1 (COI), and control region (D-Loop)]. Low genetic diversity (d<0.9, π<0.005) and average divergence (<0.6%) in mtDNA were observed among the specimens examined. The haplotypes are distributed throughout the areas sampled; therefore, no areas where individuals showed genetic identity, with exclusive haplotypes, were found. Heteromys nelsoni populations have undergone a very recent demographic contraction and the low genetic diversity observed indicates an unfavorable future for the species. Changes in the climatic conditions coupled with other anthropogenic pressures have likely reduced the optimal habitat area for the species. It is imperative to develop programs aiming to reduce the probable risk of extinction of this species.

Nomenclatural change of Chaetodipus dalquesti

ABSTRACT. The pocket mouse from the southern Baja California peninsula, Chaetodipus dalquesti, is synonymized to Chaetodipus ammophilus, following the Principle of Priority of the Code of Zoological Nomenclature, because C. ammophilus was described before C. dalquesti. The subspecies are reassigned.

Peromyscus guardia (Rodentia: Cricetidae)

Abstract Peromyscus guardia Townsend, 1912 is a small, gray-brown cricetid commonly called the La Guarda deermouse. It is a Mexican endemic rodent from Angel de la Guarda Island and 2 islets off the northern tip of Angel de la Guarda in the Gulf of California. Populations of P. guardia were common up until the mid-1960s but have since declined. This species is currently listed as “Critically Endangered” by the International Union for Conservation of Nature and Natural Resources.

Prevalence and intensity of flea Tunga monositus (Siphonaptera) in an insular population of Peromyscus maniculatus (Rodentia) from Northwest Mexico

Abstract We surveyed the status of the endemic deer mouse Peromyscus maniculatus exiguus from San Martin Island, Baja California, Mexico where the population is numerous. A total of 89 adult rodents of P. m. exiguus were caught, 51 of which were parasitized by the flea Tunga monositus (Siphonaptera: Pulicidae); prevalence was 57% and the mean infection intensity was 1.8 parasites per host. No significant differences in prevalence were found between both sexes and between sites. Our results showed a higher infection percentage than those reported in previous studies for the species.

Geographical extension of Chaetodipus fallax (Rodentia: Heteromyidae) in the Baja California Peninsula

Abstract We report two new locations for Chaetodipus fallax (Merriam 1889) in Baja California Sur, Mexico: the first, south of San Ignacio; and the second, in the plains of Magdalena Bay. These are the southernmost records for the presence of this species and broaden the species’ previously known distribution range in ~400 km. We suggest that changes in weather conditions could explain the southward expansion of the distribution of C. fallax in Baja California Peninsula.

First Record of Leucism in the Genus Peromyscus (Mammalia: Rodentia)

ABSTRACT. Leucism is a partial hypopigmentary congenital disorder previously recorded in several species of mammals. This abnormal coloration is unusual in the wild. In August 2013, in Baja California, México, we collected 2 Peromyscus fraterculus (one female and one male) exhibiting leucism. Leucism has not been previously reported in the genus Peromyscus; therefore, we documented the first known record. Leucism is expressed in natural populations having low genetic diversity and may increase selective pressure on affected individuals.