Abstract
Amphibians comprise over 7000 extant species distributed in almost every ecosystem on every continent except Antarctica. Most species also show high specificity for particular habitats, biomes, or climatic niches, seemingly rendering long-distance dispersal unlikely. Indeed, many lineages still seem to show the signature of their Pangaean origin, ~300Ma later. To date, no study has attempted a large-scale historical-biogeographic analysis of the group to understand the distribution of extant lineages. Here, I use an updated chronogram containing 3309 species (~45% of extant diversity) to reconstruct their movement between 12 global ecoregions. I find that a Pangaean origin and subsequent Laurasian and Gondwanan fragmentation explains a large proportion of patterns in the distribution of extant species. However, dispersal during the Cenozoic, likely across land bridges or short distances across oceans, has also exerted a strong influence. Finally, there are at least three strongly supported instances of long-distance oceanic dispersal between former Gondwanan landmasses during the Cenozoic. Intermediate extinction from intervening areas seems to be a strong factor in shaping present-day distributions. Both dispersal and intermediate extinction are apparently tied to the evolution of extraordinarily adaptive expansion-oriented phenotypes (allowing lineages to easily colonize new areas and speciate), or conversely, to extremely specialized phenotypes or heavily relictual climatic niches that result in strong geographic localization and limited diversification.