Abstract

The pattern of species richness and its potential causes are fundamental knowledge for an adequate management of biodiversity. In the present study, based on georeferenced lacustrine zooplankton, we evaluated the general species richness pattern and its relationship with hydrographic zonation, assessing four hypotheses: (1) the Rapoport latitudinal effect; (2) geometric restrictions as hard limits to geographical dispersion; (3) nestedness as a measure of the historical dynamics of extinction-colonization; and (4) environmental variables, as a measurement of the habitat as a recent ecological factor. Our results show a heterogeneous species richness pattern, with maxima located between 32-34 degrees S, showing a general decrease towards higher latitudes. However, this pattern does not relate to the Rapoport latitudinal effect or the geometric restrictions. Instead, the pattern is associated with historical extinction-colonization dynamics between the waterbodies and ecological factors such as landscape, water, and energy availability that determine the number of species that these waterbodies can currently support.