Irene Goyenechea

Beta Diversity in a Highly Heterogeneous Area: Disentangling Species and Taxonomic Dissimilarity for Terrestrial Vertebrates

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.

Taxonomic status of the snake genera Conopsis and Toluca (Colubridae)

The taxonomic history of the colubrid genera Conopsis and Toluca is complex and has been reviewed by Goyenechea and Flores-Villela (2000). The single character purportedly differentiating them has been called into question by several authors (e.g., Bogert and Oliver, 1945). Some workers recognize just one genus for this group (Bogert and Oliver, 1945; Goyenechea, 1995), whereas others have regarded the two genera as valid (Boulenger, 1894; Duges, 1896; Duellman, 1961). Taylor and Smith (1942) reviewed these genera and concluded that each was valid. According to these authors, species of Toluca have a groove on each posterior maxillary tooth, that is lacking in species of Conopsis. In spite of the review by Taylor and Smith (1942), the generic status of Conopsis and Toluca was questioned by Bogert and Oliver (1945) because the latter did not consider the putative diagnostic character sufficient for recognizing the genus Toluca. In addition to the presence or absence of grooves in the posterior maxillary teeth, another morphological character purportedly differentiating these genera is the condition of the loreal scale (Taylor and Smith, 1942). In Conopsis, the loreal scale may be present or fused with the nasal, whereas it is completely absent in Toluca. As part of revisionary work on these snakes, we reevaluated these putative, diagnostic features in all recognized taxa of both genera to assess their taxonomic utility, since the only way to allocate specimens to particular species has been on the basis of geographic provenance. We examined 659 museum specimens, including 199 Conopsis and 460 Toluca that represented all known taxa (10 species and subspecies) from throughout the geographical range of both genera (both are endemic to Mexico, distributed from Chihuahua to Oaxaca), in order to reevaluate their taxonomic status. The following characters were recorded: snout-vent length (SVL), total length (TL), diameter of the body (DIAM), number of ventral and subcaudal scales, supralabials, infralabials, presence-absence of the nasal, loreal, preocular, postocular, frontal, and genial scales, temporal formula, shape of the hemipenis, and dorsal and ventral color pattern. To determine the presence or absence of tooth grooves, maxillae were dissected on 43 specimens (Appendix 1) representing all recognized species and subspecies of each genus. One maxilla

Designation of a Neotype for Conopsis nasus (Serpentes: Colubridae)

Abstract The designation of a neotype for Conopsis nasus is necessary because the type specimen is apparently lost, the original description is ambiguous and can be applied to more than one valid taxon, and there are inconsistencies with the previous designation of type locality. The neotype is chosen from the herpetological collections at the British Museum of Natural History and shows the typical characters as defined in the original description as well as the diagnostic characters for the species defined in a recent study.

Evidence of niche shift and invasion potential of Lithobates catesbeianus in the habitat of Mexican endemic frogs

Invasive alien species are one of most severe threats to biodiversity and natural resources. These biological invasions have been studied from the niche conservatism and niche shifts perspective. Niche differentiation may result from changes in fundamental niche or realized niche or both; in biological invasions, niche differences between native and non-native ranges can appear through niche expansion, niche unfilling and niche stability. The American bullfrog Lithobates catesbeianus is an invasive species that can have negative impacts on native amphibian populations. This research examines the climate niche shifts of this frog, its potential range of expansion in Mexico and the risk of invasion by bullfrog in the habitats of 82 frog species endemic to Mexico, that based on their climatic niche similarity were divided in four ecological groups. The results indicate that species in two ecological groups were the most vulnerable to invasion by bullfrog. However, the climate niche shifts of L. catesbeianus may allow it to adapt to new environmental conditions, so species from the two remaining groups cannot be dismissed as not vulnerable. This information is valuable for decision making in prioritizing areas for conservation of Mexican endemic frogs.

Distribution Patterns of the Mexican Species of Carrion Beetles (Coleoptera: Silphidae)

Abstract Silphidae in Mexico, as in other countries, are a broadly studied family of Coleoptera. However, their geographical distribution in this country has been poorly analyzed. The aim of this study was to perform a track analysis of the Mexican species of Silphidae to discuss their distribution patterns. We used bibliographic and new distribution data of 11 Mexican species of Silphidae to construct their individual tracks in maps of biogeographic provinces. The superposition of these tracks allowed detection of generalized tracks, which were compared with previously published distribution patterns to propose hypotheses of primary biogeographic homology. We record Nicrophorus olidus Matthews, 1888 for the first time in Nicaragua and confirm its presence in Honduras. Additionally, three species are new state records for Aguascalientes, and new localities are provided for seven species. We recovered three main distribution patterns. Four species correspond to the Californian Nearctic pattern, followed by the continental Nearctic plus the montane Mexican pattern represented by three species, and the Mesoamerican plus the montane Mexican pattern constituted by two species. Each of the last two species showed a unique distribution. Seven of the 11 Mexican silphid species show Nearctic affinity, three have a Neotropical affinity, and one is endemic to the montane Mexican component. Patterns detected for Mexican silphids have been documented for other families of Coleoptera, thus they can be postulated as hypotheses of biogeographic primary homology. These hypotheses should be tested with other biological groups, and their causes need to be investigated with different historical biogeographical methods.