Origin, evolution and diversification of extant amphibians

Abstract

Amphibians constitute one of the major branches of the vertebrate tree of life, with nearly 8,400 extant species currently inhabiting most terrestrial and freshwater habitats in temperate and tropical landmasses worldwide. The extant amphibians (Lissamphibia) encompass three orders of markedly distinct morphologies and life styles. The most diverse of these are the Anura (frogs and toads) that have short, tailless bodies with long, powerful hind limbs for jumping. Less diverse Caudata (salamanders and newts) have slender bodies with proportionally paired limbs and long tails. And the smallest group are the Gymnophiona (caecilians) that have elongated, limbless bodies adapted for burrowing. Extant amphibians have a long evolutionary history that probably extends back more than 300 million years ago, and are key for understanding the colonization of terrestrial environments by early tetrapods. This chapter discusses the state-of-knowledge of the origin and ancestry, phylogeny and evolution, and diversification of extant amphibians. Since the beginning of the XXI century, the vast accumulation of data from multiple sources (molecular, genomic, paleontological, morphological, ecological, behavioural, biogeographical) as well as the spread of integrative approaches have shed light on long hotly debated issues on the origin and evolution of this important group of vertebrates.