PHYLOGENETIC RELATIONSHIPS OF THE SALAMANDER FAMILIES: AN ANALYSIS OF CONGRUENCE AMONG MORPHOLOGICAL AND MOLECULAR CHARACTERS

Abstract

The phylogenetic relationships of the ten salamander families (Ambystomatidae, Amphiumidae, Cryptobranchidae, Dicamptodontidae, Hynobiidae, Plethodontidae, Proteidae, Rhyacotritonidae, Salamandridae and Sirenidae) were examined using 209 phylogenetically infor- mative characters, including 177 from ribosomal RNA sequence variation, 20 from head and trunk morphology, and 12 from cloacal anatomy. Our analysis invokes the principle of "total evidence" by combining all relevant data to generate a phylogeny, and then examining patterns of character congruence on that phylogeny. The morphological and molecular data sets were not highly incon- gruent; only 4-26% of the total incongruence among characters occurs between the morphological and molecular data sets and the remainder occurs within them. The combined analysis differs from an earlier analysis of the molecular data alone primarily by favoring monophyly of the internally fertilizing salamanders. Our favored working hypothesis of salamander family relationships places the Sirenidae as the sister group to all remaining salamanders, and the Cryptobranchoidea (Cryp- tobranchidae and Hynobiidae) as the sister group of the internally fertilizing salamanders (all remaining families). Among the internally fertilizing families, the Ambystomatidae and Dicamp- todontidae are closely related and form a sister group to the Salamandridae; the Proteidae (rep- resented by the genus Necturus) is the sister group to these three families combined. The Am- phiumidae, Plethodontidae and Rhyacotritonidae represent early branching events within the clade containing the internally fertilizing salamanders. New molecular data on hynobiids (including the genera Batrachuperus, Hynobius, Onychodactylus and Salamandrella) are compatible with mono- phyly of the Hynobiidae.