ABSTRACT
Freshwater crabs are a large group of aquatic animals, with more than 1,280 described species worldwide found in freshwater ecosystems throughout the warmer parts of the Neotropical, Afrotropical, Palaearctic, Oriental, and Australasian zoogeographical regions. We report here on the changes in the understanding of the higher systematics of these decapods over the past 25 years associated with attempts to put freshwater crab taxonomy into a phylogenetic framework. The distributional patterns of the freshwater crabs on continents and islands are interpreted in terms of their dispersal abilities and barriers to their distribution. Theories on freshwater crab origins are discussed in the light of their phylogeny and present-day distributions. Adaptations to a permanent existence in freshwater and the adaptive radiation of freshwater crabs into such ecosystems worldwide are discussed.
