Desde hace 10 años en que se publicó el trabajo de Ramírez-Pulldo et al. (1983), no se ha presentado una lista completa de las especies y subespccies de los mamíferos terrestres de México y en la cual se incorporen los cambios taxonómicos efectuados. Si bien es cierto queen trabajos posteritíres (Ramírez-Pulidoetal., 1986y Ramírez-PulidoyCastro-Campillo, 1990) se mencionaron los cambios taxonéimicos y las nuevas categorías específicas y subespecíficas que fueron publicados durante los lapsos respectivos, la forma como se ha presentadoesa información noperrnite identificar con prontitudladiversidad mastozoológica mexicana.
We present a molecular phylogeny of North American species of long-tailed shrews of the genus Sorex. Our focus is on Mexican and Guatemalan species to begin understanding their evolutionary relationships and to test the validity of nominal species. Seventy-seven sequences of the mitochondrial cytochrome b gene were analyzed, including 19 specimens representing nine Mexican and one Guatemalan species. Phylogenetic analyses using parsimony, maximum likelihood and Bayesian approaches revealed two major clades of North American species, all within the subgenus Otisorex. The first major clade includes S. trowbridgii and southern species (S. macrodon from Oaxaca; S. veraecrucis from Nuevo León, Michoacán, Chiapas, S. saussurei from Jalisco and Guatemala; S. veraepacis from Guerrero and Guatemala). Relatively deep branches among taxa characterize this clade and suggest that their early divergence from other North American shrews was soon after arrival of the ancestral stock from the Beringian region. The other major clade includes all other North American species of Sorex we examined, with two Mexican species, S. milleri and S. emarginatus, grouped in a subclade with the S. cinereus complex. Sorex veraecrucis is not, however, a monophyletic taxon because specimens of this nominal species were included in both the major clades. The Isthmus of Tehuantepec has likely played a role as a biogeographic barrier in the evolutionary history of Mexican shrews. This study of mitochondrial variation in southern North American shrews of the genus Sorex indicates there is substantial, previously undetected diversity that necessitates a revision of the taxonomy of S. veraecrucis and S. veraepacis.
Se analizaron datos sobre densidad poblacional de la liebre de Tehuantepec, Lepus flavigularis durante seis años de monitoreo en las poblaciones de Montecillo Santa Cruz y San Francisco del Mar Viejo, al sur del Istmo de Tehuantepec, Oaxaca, México. Se calculó el índice de fluctuación poblacional (IF) para esta especie de lagomorfo en las dos localidades. Los intervalos en fluctuación entre niveles poblacionales máximos y mínimos fueron evaluados de acuerdo al número promedio de años requeridos para que los cambios ocurran. Se llevó a cabo el método de transecto de ancho fijo para la obtención de valores de densidad. La liebre de Tehuantepec presenta en general, valores en densidad bajos en ambas poblaciones de estudio, con IF altos en Montecillo Santa Cruz, lo que indica que presenta una gran amplitud de cambios en su tamaño poblacional en periodos de tiempo cortos, debido probablemente a las prácticas de uso de suelo de la zona, mismas que incluyen una intensa ganadería extensiva y la aplicación de quemas controladas. En San Francisco del Mar Viejo, zona con menor intensidad de pastoreo y sin quemas, la liebre de Tehuantepec presentó valores de IF bajos, por lo que es probable que en esta población la especie se mantenga más estable a lo largo del tiempo.
Mexico is considered a mammal diversity hotspot, and most conservation efforts involving mammals focus on large and charismatic species. Herein, we provide an assessment of the conservation status of species that are often overlooked in conservation programs, Mexican rodents of the families Geomyidae (pocket gophers) and Heteromyidae (pocket mice and kangaroo rats). Based on distributional maps and recent systematic studies, a taxonomic and biogeographical distributional checklist was made. The conservation lists of the International Union for Conservation of Nature and the Mexican Secretaría de Medio Ambiente y Recursos Naturales were used to identify 8 geomyid species, and 8 species and 27 subspecies of heteromyids as endangered. Major threats to their conservation are change in land use, destruction of habitat and a lack of knowledge about their current distribution and population trends.
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