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

Tania Escalante, Gerardo Rodríguez-Tapia, Miguel Linaje, Juan J. Morrone, Elkin Noguera-Urbano
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Journal Article
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We analyzed whether the spatial variation in mammal species richness reflects the southern bounda- ries 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 spe- cies 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 distribu- tions. 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 Nearc- tic 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 rich- ness shows the classical latitudinal diversity gradient, with the number of species increasing to the tropics. We conclude that the Nearctic region has a low mam- mal richness, with a richness pattern corresponding with previously described patterns of endemism, with a boundary situated at 26 ° – 30 ° latitude. Keywords:

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