Quantifying differences in species composition among communities provides important information related to the distribution, conservation and management of biodiversity, especially when two components are recognized: dissimilarity due to turnover, and dissimilarity due to richness differences. The ecoregions in central Mexico, within the Mexican Transition Zone, have outstanding environmental heterogeneity and harbor huge biological richness, besides differences in the origin of the biota. Therefore, biodiversity studies in this area require the use of complementary measures to achieve appropriate information that may help in the design of conservation strategies. In this work we analyze the dissimilarity of terrestrial vertebrates, and the components of turnover and richness differences, among six ecoregions in the state of Hidalgo, central Mexico. We follow two approaches: one based on species level dissimilarity, and the second on taxonomic dissimilarity. We used databases from the project “Biodiversity in the state of Hidalgo”. Our results indicate that species dissimilarity is higher than taxonomic dissimilarity, and that turnover contributes more than richness differences, both for species and taxonomic total dissimilarity. Moreover, total dissimilarity, turnover dissimilarity and the dissimilarity due to richness differences were positively related in the four vertebrate groups. Reptiles had the highest values of dissimilarity, followed by mammals, amphibians and birds. For reptiles, birds, and mammals, species turnover was the most important component, while richness differences had a higher contribution for amphibians. The highest values of dissimilarity occurred between environmentally contrasting ecoregions (i.e., tropical and temperate forests), which suggests that environmental heterogeneity and differences in the origin of biotas are key factors driving beta diversity of terrestrial vertebrates among ecoregions in this complex area.

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The Santa María Amajac paleolake is located in the central portion of Hidalgo, Mexico. Twenty-seven fossil taxa of aquatic and terrestrial plants, gastropods, ostracods, amphibians, and mammals identified previously in the area of the paleolake were selected and their distribution in America during the Late Pliocene-Pleistocene was analyzed using the panbiogeographic method. As a result of the overlap of 27 individual tracks, 5 generalized tracks were obtained: I) Western North American, II) Central North American, III) Eastern North American, IV) Mesoamerican, and V) South American. The generalized tracks are consistent with previous proposals for extant gymnosperms, amphibians, sauropsids, birds, mammals, aquatic plants, insects, beetles, and nematodes, suggesting that distribution patterns have prevailed since the late Pliocene (Blancan). Four biogeographic nodes were identified, 2 situated in North America, in California and Colorado, the third located in the Santa María Amajac area in central Mexico, and the fourth located in Central America.

Se estudiaron la riqueza y la distribución de los anfibios y saurópsidos no aves de las 2 ecorregiones áridas de Hidalgo. Para ello, se realizó un listado taxonómico con información bibliográfica y de campo, se analizó la complementariedad entre ecorregiones y se comparó la composición de especies contra 5 zonas áridas de México. Además, se analizaron los atributos de historia natural de las especies, el estatus de conservación y el endemismo. Se registran 82 especies: 20 anfibios y 62 saurópsidos no aves. La ecorregión matorral central mexicano presentó la mayor riqueza con 65 especies: 29 exclusivas y 36 compartidas con la ecorregión matorral de la meseta central. Se registraron 62 especies en el matorral xerófilo, 2 en el bosque tropical caducifolio y 18 en ambos tipos de vegetación. La complementariedad entre ecorregiones fue de 55 para anfibios y 32.07 para saurópsidos no aves. La mayor similitud (52.4) se presentó con la zona árida de Querétaro. La mayoría de las especies son terrestres, insectívoras y ovíparas. Se registraron más anfibios nocturnos y más saurópsidos no aves diurnos. Finalmente, 18 especies se encuentran bajo protección especial, 16 amenazadas y 44 son endémicas de México. Derechos Reservados © 2015 Universidad Nacional Autónoma de México, Instituto de Biología. Este es un artículo de acceso abierto distribuido bajo los términos de la Licencia Creative Commons CC BY-NC-ND 4.0.

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