Global diversity of amphibians (Amphibia) in freshwater
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This article present a review of species numbers, biogeographic patterns and evolutionary trends of amphibians in freshwater. Although most amphibians live in freshwater in at least their larval phase, many species have evolved different degrees of independence from water including direct terrestrial development and viviparity. Of a total of 5,828 amphibian species considered here, 4,117 are aquatic in that they live in the water during at least one life-history stage, and a further 177 species are water-dependent. These numbers are tentative and provide a conservative estimate, because (1) the biology of many species is unknown, (2) more direct-developing species e.g. in the Brachycephalidae, probably depend directly on moisture near water bodies and (3) the accelerating rate of species discoveries and descriptions in amphibians indicates the existence of many more, yet undescribed species, most of which are likely to have aquatic larvae. Regional endemism in amphibians is very high, with only six out of 348 aquatic genera occurring in more than one of the major biogeographic divisions used herein. Global declines threatening amphibians are known to be triggered by an emerging infectious fungal disease and possibly by climate change, emphasizing the need of concerted conservation efforts, and of more research, focused on both their terrestrial and aquatic stages.