Evolution of Viviparity in Salamanders (Amphibia, Caudata)

Abstract Reproductive modes in salamanders (Amphibia, Caudata) are highly diverse. Viviparity, for instance, implies the retention of the developing embryos inside the females until the end of the gestation, at which point they deliver fully developed terrestrial juveniles. From an ecological point of view, the evolution of viviparity is highly significant, since it implies the semi‐independence of water for an amphibian. Nevertheless, viviparity is not very common among salamander. It has independently evolved only in a few species, all included within the family Salamandridae. Furthermore, the characteristics of viviparous strategies are different among species, although they all share some commonalities. The detailed study of these particular and common features in a phylogenetic context will reveal the genetic, physiological, developmental, morphological and historic factors that have triggered the evolution of this peculiar mode of reproduction in only one lineage among all the species of salamanders. Key Concepts: Viviparity entails the complete development of the progeny within the mother's genital tract, together with the maternal provisioning of nutrients to the embryos. Since development occurs within the females, viviparity in amphibians implies that the aquatic phase of the standard amphibian life cycle is obviated in viviparous species. Viviparity has independently evolved only in a few species of salamanders.