Searching the Spectrum of Frogs

Frog skeletons

When William Duellman joined the KU staff in 1959, the herpetology collection had 50,000 specimens; today there are 320,000 frogs, lizards, and snakes — thousands of these collected by Duellman himself. As he traveled and collected in the southern United States and Mexico, Panama, Ecuador, Brazil, Argentina, Chile and Peru, he encountered many new species.

Duellman, herpetology curator emeritus, says that collections are essential when scientists are trying to discern whether a specimen is a new species. First, a researcher needs to compare the specimen to other similar species to ensure that it is, in fact, a new and different kind of creature. For example, if you found a two-headed turtle, you would need to compare it to other turtles to figure out if it were a new species, a rarity, or a genetic fluke.

Racks of jars

Then, to truly understand a new species, a researcher must represent the spectrum of sizes, developmental phases, eating and mating habits, and variation in coloration and internal structures. Duellman offered an example of how varied a species can be: "If you were trying to describe a human being, and the only specimen you had was Arnold Schwarzenegger, well, that wouldn’t tell you very much about me, would it?" he joked.

Duellman knows how important it is to hold on to every single specimen. In 2002, one of Duellman’s colleagues found a tiny juvenile frog on a mountain in the South American country Guyana. The frog "didn’t resemble anything I’d ever seen before," Duellman said. He studied its morphology, while colleagues at Pennsylvania State analyzed its DNA. By both accounts, the unknown little frog seemed to be in a genetic family all its own. But because the team had only one specimen, the idea was impossible to prove. The frog’s place in the tree of life remained a question mark.

In 2007, another researcher found two other frogs similar to the unidentified one. Duellman again studied their physical features closely — even looking at MRI’s of their skeletal features — and sent tissues to the group at Pennsylvania State for DNA analysis.

With the new specimens, Duellman and colleagues were able to erase the question mark. The three frogs indeed belonged to a new family, which they named Ceuthomantidae. And what’s more, this new family was the earliest evolved frog in its clade, or subset, of the evolutionary tree.