A Phylogeny of Mexican Ambystoma Salamanders (Caudata: Ambystomatidae) from Larval Characters

A phylogeny of Mexican Ambystoma salamanders was constructed using
larval morphology. Characters were scored for 19 ambystomatid species from
Mexico and North America Twenty-five continuous characters came from
external measurements of cranial and branchial features and ratios of
measurements. Twenty-six categorical characters were scored from internal and
external larval, branchial, and cranial features, as well as overall color and adult
life history. Cladograms constructed from individual character matrices lack
major resolution beyond individual species level. The consensus cladogram did
not resolve the majority of species, and was similar to consensus results from
previous cladistic analysis based on molecular characters. Convergent
morphology is evident in characters of geographically distant members of the
clade. However, species determination was possible for all examined taxa.
Neoteny is widespread in the A. tigrinum complex and, as an isolating
mechanism, may be the main driver of speciation in the complex.