Species composition, biogeography, and conservation of the Caatinga lizards

Abstract

The Caatinga is one of the few semiarid regions in the subtropical zone surrounded by humid areas. Its fauna was previously considered impoverished and with few endemics, but many surveys have been conducted in the last two decades and it is now possible to perform a more accurate and realistic analysis of Caatinga lizard diversity and biogeography. Our objectives in the present chapter are to (1) review the literature on the origin and diversification of Caatinga lizards; (2) provide an updated species list and categorize distribution patterns; (3) identify potential areas that could hold high species richness; and (4) evaluate whether the proposed division of the Caatinga into different ecoregions reflects patterns of lizard endemism. We found 79 lizard species belonging to 13 families. Among them, 49 are typical from the Caatinga, eight occur in forested habitats, nine are typical from Cerrado habitats, three are endemic to humid forest enclaves ('brejos de altitude') and eight occur only in rocky outcrops from the Espinhaço Mountain Range. The areas of endemism recovered corroborate most of the proposed ecoregions, and the most diverse areas are at the marginal portions of the Caatinga, with nuclear areas showing lower richness potentials. We identified 38 endemic species most from paleoclimatic dunes from São Francisco River and 'Raso da Catarina'. We can now confirm that previous suggestions about the Caatinga fauna being species poor and having low endemism are not correct. It is clear that the Caatinga shares part of its fauna with Cerrado, Atlantic Forest, and even with Chaco, but the number of endemics is relatively high and still rising as new data become available. With the results generated here we indicate some directions for future studies and conservation priorities.