The study's DNA research revealed that, while many ocean dispersals may have occurred over time, only two led to the current faunas: one for the Caribbean islands and another for Central America. The scientists speculate that it may not be coincidental that these ancient and successful dispersals happened after the asteroid collision rather than earlier. "The asteroid impact generated giant waves that devastated the islands, probably eliminating any existing fauna at that time," Hedges said.
The original frogs that successfully colonized the Caribbean islands likely hitched a ride on floating mats of vegetation called flotsam, which is the method typically used by land animals to travel across salt water. "Some rafts of flotsam, if they are washed out of rivers during storms and caught in ocean currents, can be more than a mile across and could include plants that trap fresh water and insect food for frogs," Hedges said. It is not likely that the frog species dispersed simply by swimming because frogs dry easily and are not very tolerant of salt water.
In addition to the study's discoveries about Caribbean and Central American frogs, the research also revealed and defined an unusually large and unpredicted group of species in South America. "The South American group may have more than 400 species and is mostly associated with the large Andes mountains of South America," Hedges said.
"Until now, the entire group of these terrestrial, tropical frog species -- the eleutherodactylines -- have been considered a "black hole" in amphibian biology because of the poor understanding of their evolutionary history," explained Hedges. Scientists consider the knowledge of evolutionary relationships, also called "phylogeny," to be fundamental to many fields of biology, including medicine, a