Gerardo Rodríguez-Tapia

Identification of areas of endemism from species distribution models: threshold selection and Nearctic mammals

We evaluated the relevance of threshold selection in species distribution models on the delimitation of areas of endemism, using as case study the North American mammals. We modeled 40 species of endemic mammals of the Nearctic region with Maxent, and transformed these models to binary maps using four different thresholds: minimum training presence, tenth percentile training presence, equal training sensitivity and specificity, and 0.5 logistic probability. We analyzed the binary maps with the optimality method in order to identify areas of endemism and compare our results regarding previous analyses. The majority of the species tend to have very low values for the minimum training presence, whereas most of the species have a value of the tenth percentile training presence around 0.5, and the equal training sensitivity and specificity was around 0.3. Only with the tenth percentile threshold we recovered three out of the four patterns of endemism identified in North America, and detected more endemic species.The best identification of areas of endemism was obtained using the tenth percentile training presence threshold, which seems to recover better the distributional area of the mammals analyzed.

Climate-Induced Range Shifts and Possible Hybridisation Consequences in Insects

Many ectotherms have altered their geographic ranges in response to rising global temperatures. Current range shifts will likely increase the sympatry and hybridisation between recently diverged species. Here we predict future sympatric distributions and risk of hybridisation in seven Mediterranean ischnurid damselfly species (I. elegans, I. fountaineae, I. genei, I. graellsii, I. pumilio, I. saharensis and I. senegalensis). We used a maximum entropy modelling technique to predict future potential distribution under four different Global Circulation Models and a realistic emissions scenario of climate change. We carried out a comprehensive data compilation of reproductive isolation (habitat, temporal, sexual, mechanical and gametic) between the seven studied species. Combining the potential distribution and data of reproductive isolation at different instances (habitat, temporal, sexual, mechanical and gametic), we infer the risk of hybridisation in these insects. Our findings showed that all but I. graellsii will decrease in distributional extent and all species except I. senegalensis are predicted to have northern range shifts. Models of potential distribution predicted an increase of the likely overlapping ranges for 12 species combinations, out of a total of 42 combinations, 10 of which currently overlap. Moreover, the lack of complete reproductive isolation and the patterns of hybridisation detected between closely related ischnurids, could lead to local extinctions of native species if the hybrids or the introgressed colonising species become more successful.

Delimitation of the Nearctic region according to mammalian distributional patterns

Abstract The Nearctic has been recognized as a biogeographic region since the 19th century. We analyzed distributional patterns of the mammals inhabiting North and Central America, from Alaska to Panama, to delimit the boundaries of the Nearctic region. We performed 6 optimality analyses, using a grid of 4° latitude–longitude, based on families, genera, species, and combinations of these. The analysis of the matrix with the 3 taxonomic levels yielded better results in terms of the largest number of endemics and the best delimitation of the Nearctic region. We also found 3 patterns—western, eastern, and northern—within the region that coincide partially with previous biogeographic characterizations. Although mammals seem to represent appropriate taxa to delimit this region, we conclude that a more robust delimitation might be obtained by analyzing other plant and animal taxa.

Mexican biogeographic provinces: Map and shapefiles

We provide a map of the 14 biogeographic provinces of Mexico based on the ecoregions recognized for the country, which combine climatic, geological and biotic criteria. These provinces belong to the Nearctic region (Californian, Baja Californian, Sonoran, Chihuahuan Desert and Tamaulipas provinces), Neotropical region (Pacific Lowlands, Balsas Basin, Veracruzan and Yucatán Peninsula provinces) and the Mexican transition zone (Sierra Madre Occidental, Sierra Madre Oriental, Transmexican Volcanic Belt, Sierra Madre del Sur and Chiapas Highlands provinces). In order to facilitate future biogeographic analyses, we provide a file of the biogeographical regionalisation of Mexico by converting the map into a polygon shapefile and a raster file with all provinces. We also separately provide each of the provinces in vector and raster format. All the maps are in geographical and Lambert Conformal Conic projections.

Mammal species richness and biogeographic structure at the southern boundaries of the Nearctic region

Abstract We analyzed whether the spatial variation in mammal species richness reflects the southern boundaries of the Nearctic region as previously established by endemism patterns. Records from 710 mammal species were drawn on a map of North America (from Canada and Alaska to Panama) gridded at 4° latitude-longitude. We evaluated the probable existence of unknown species through three richness estimators (Chao2, ICE, and Jack1), modeled the potential distribution of species, and mapped the predicted pattern of species richness through the number of coexisting potential distributions. The poorest grid cells are in the northern areas, whereas the richest ones are in the southern areas, coinciding with the pattern of collecting points. The average richness of 4° grid cells comprising the Nearctic region was 18 species, and the richest 4° grid cells had 150 species, coinciding with the 26° latitude. From the 406 mammal species of the Nearctic region, 104 are restricted to it, and 305 species situated south of it are not distributed in the region. The map of predicted richness shows the classical latitudinal diversity gradient, with the number of species increasing to the tropics. We conclude that the Nearctic region has a low mammal richness, with a richness pattern corresponding with previously described patterns of endemism, with a boundary situated at 26°–30° latitude.