Hence the surprise when a new University of California, Berkeley, study of the largest family of salamanders produced a genetic family tree totally inconsistent with the accepted classification, which is based primarily on physical features.
Salamanders formerly classified together because of similar characteristics, such as a tail that breaks at only one spot as opposed to anywhere when stressed, now appear not to be close relatives at all. And salamanders that go through an aquatic larval stage are scattered about on different branches instead of grouped on one limb of the tree: Apparently some salamander lineages lost the larval stage and then reacquired it again.
"For 40 years, we have had a very clear understanding of the evolutionary history of the largest family of salamanders, Plethodontidae," said David Wake, professor of integrative biology at UC Berkeley and an expert on salamanders. "We thought they arose in Appalachian mountain streams and then diverged in a highly patterned way, sequentially abandoning larvae for direct development, gaining highly specialized, projectile tongues, et cetera."
"The results were stunningly different than what we anticipated," he said. "Only one of the currently recognized four major groups is supported."
The study, published this week in the online edition of the Proceedings of the National Academy of Sciences, was conducted by Wake's graduate student, Rachel Mueller, to understand the evolution of the Plethodontid salamanders, a family that comprises 360 species - two-thirds of the world's 522 known species of salamander. Known for being one of few landlubbing verteb
Contact: Robert Sanders
University of California - Berkeley