Biogeography, vicariance and conservation of snakes of the neglected and endangered Caatinga region, north-eastern Brazil

Aim Our aims were to test the predictions of the vicariance model, searching for natural, non-random biogeographical units using data on snake distributions, and to assess the conservation of biogeographical patterns and underlying processes in the poorly studied Caatinga region. Location Caatinga region, north-eastern Brazil. Methods We revised and georeferenced 7352 snake occurrence records at point localities, by direct examination of voucher specimens in zoological collections and revision of literature data. We tested two predictions of the vicariance model via biotic element analysis using two datasets (all taxa and endemics) mapped onto a 1 degrees x1 degrees square grid across the Caatinga. Finally, we examined the overlap between recovered biogeographical units and spatial patterns of habitat loss and protected area coverage. Results We recorded 112 snake species from the Caatinga, of which 22 (20%) are endemics. The predictions of the vicariance model were corroborated by the detection of groups of species with significantly clustered ranges (biotic elements). The analysis with the full dataset detected eight biotic elements, and three endemic biotic elements were found when only using endemics. The three endemic biotic elements correspond to core areas of biotic elements detected with the larger dataset. The average habitat loss for species forming biotic elements was 46%, and was similar among biotic elements. Protected area coverage is different for species from different biotic elements, and most species' ranges are very poorly represented in protected areas. Main conclusions The Caatinga harbours a peculiar snake fauna with significantly clustered species ranges concordant with the predictions of the vicariance model. Our results, representing the first formal test of vicariance patterns in the Caatinga, detected poor overlap between biotic elements and protected areas, indicating that biogeographical patterns and processes are largely unprotected in this imperilled and neglected Neotropical region.