Turnover patterns in bats related to areas of endemism in Northwestern Argentina

FERRO L. I,; M.L. SANDOVAL; M.I. MOLLERACH; R.M. BARQUEZ

San Javier, Tucumán, Argentina

Congreso; Meeting of the Willi Hennig Society; 2008

Willi Hennig Society

Bats are used to characterize areas of endemism in the Yungas forest of Northwestern Argentina. An area of endemism (AE) is defined by the congruent distribution of two or more species spatially restricted to that area. Then, an AE should exhibit high homogeneity of the distributional ranges of its biotic elements, with respect to neighbouring areas. Thus, high rates of species turnover and/or pronounced gradients of richness are expected in transitional zones between AEs, as a consequence of abrupt changes in the patterns of species distribution. We analyze here the geographical distribution of 42 species of bats from northwestern Argentina. We used more than 1000 georeferenced records and square grids with cells of 0.5 and 0.25 . To measure the species turnover we used Whittaker’s index (WI) and the density of distributional range edges per cell (DDR). The correspondence between edges of AEs obtained by an optimality criterion and the patterns of species’ turnover were evaluated by superimposing maps. Both WI and DDR showed high values on the margins of the AE of the northern Yungas. In particular, DDR reached the highest values all along the western margin of the AE of the northern and southern Yungas. There is a sharp elevation gradient in these areas that probably limits the distribution of the majority of the species. In the eastern border, however, the DDR was lower and the gradient of richness was less pronounced. In the eastern border the value of WI was high in both AEs of the northern and southern Yungas. The western edge of the AE of the Yungas is then characterized by an abrupt gradient of species richness, while the eastern edge is dominated by the high species turnover rates. . To measure the species turnover we used Whittaker’s index (WI) and the density of distributional range edges per cell (DDR). The correspondence between edges of AEs obtained by an optimality criterion and the patterns of species’ turnover were evaluated by superimposing maps. Both WI and DDR showed high values on the margins of the AE of the northern Yungas. In particular, DDR reached the highest values all along the western margin of the AE of the northern and southern Yungas. There is a sharp elevation gradient in these areas that probably limits the distribution of the majority of the species. In the eastern border, however, the DDR was lower and the gradient of richness was less pronounced. In the eastern border the value of WI was high in both AEs of the northern and southern Yungas. The western edge of the AE of the Yungas is then characterized by an abrupt gradient of species richness, while the eastern edge is dominated by the high species turnover rates.