Figure 1: The tiger salamander radiation exemplifies the developmental plasticity hypothesis of ecological speciation [1315, 54]. (a) Environmentally induced alternative phenotypes of the tiger salamander (Ambystoma tigrinum) include terrestrial metamorphs and aquatic paedomorphs. (b) The California tiger salamander (A. californiense) is an obligate metamorph derived from a developmentally plastic common ancestor with A. tigrinum [55]. (c) The Mexican axolotl (A. mexicanum) is one of several obligate paedomorphs, independently derived from plastic ancestors within the last few million years [55, 57, 58].