June 11, 2007 — The same meteor impact that wreaked havoc with dinosaurs may have been the making of 162 species of Caribbean frogs, which descended from a single South American species, according to a new study.
All of the frogs are an odd sort — having no tadpole phase, instead hatching complete out of eggs. The 800 or so species of these Eleutherodactlus frogs — make up a fifth of all living frog species and compose the largest vertebrate genus.
In the world of biological classification, however, bigger is not necessarily better, explained Blair Hedges, a biologist at Pennsylvania State University.
"The reason it's been the largest genus of vertebrates is because it's a taxonomic waste can," said Hedges. "These frogs don't give you a lot of characteristics to work with." In other words, many frog species fitting the same general description were dumped into the same genus — a level of classification just above species — simply for lack of better information.
Hedges and his coworkers have used genetic analysis to re-organize the waste can into a proper map of the Eleutherodactlus family tree.
Their study, which reveals a Caribbean branch to the family tree and supports the meteor impact connection, appears in the June 12 issue of the Proceedings of the National Academy of Sciences.
"Hedges and coworkers have tackled a vexing problem," said biologist David Wake of the University of California at Berkeley. What they found is that the very large number of frogs on Caribbean islands evolved there in the last 50 million years, after an initial invasion of a single species from South America.
