Abstract
The latitudinal gradient of species diversity is a widely recognized but poorly understood phenomenon. In marine systems, differences in dispersal abilities among species may pose an additional problem in identifying the processes that affect diversity. We compared latitudinal diversity gradients along two parallel continental coasts, the east and west coasts of South America, of two groups of Crustacea (Brachyura and Anomura), which exclusively exhibit planktonic development. We also evaluated the species‐area and the energy‐input hypotheses. Diversity decreased with increasing latitude for both groups in both oceans. Results suggest that the spatial structure of sea surface temperature (SST) explains diversity of both groups at large, but not small (