A phylogeny-based analysis of ‘ecological types’ of salamander larvae (Amphibia: Caudata)

Abstract The consideration of phylogeny has revolutionized the study of adaptations in nature, often overturning long-held beliefs. One such belief that has persisted for at least a century is the idea that aquatic salamander larvae exhibit specific morphologies that are adapted for life in still vs. running waters. So-called ‘pond-type’ larvae are purported to have extensive gills and long, tall dorsal fins along the trunk and tail, whereas ‘stream-type’ larvae are characterized by small gills and low, streamlined dorsal fins restricted to the tail. We tested whether gill and dorsal-fin development represent adaptations to specific larval habitats by measuring images of 59 species of salamanders from 9 of the 10 extant families. Using a recent, comprehensive phylogeny of salamanders within a phylogenetic analysis of covariance, we determined that there is evidence of morphological adaptation of larvae to their respective habitats. However, the phylogenetic influence is so strong as to render the simple dichotomy of ‘pond-type’ vs. ‘stream-type’ larvae largely meaningless.