It’s been a good couple of weeks for herps-in-amber fans. Last week, Emma Sherratt and colleagues (including me) published a paper expanding the number of known Dominican amber anoles from 3 to 38. And now comes a paper by Poinar and Wake in the journal Palaeodiversity reporting a finding perhaps even more improbable: a fossil salamander in amber from the Dominican Republic.
What is so remarkable about this discovery is that salamanders do not occur anywhere in the Caribbean today. Indeed, salamanders are one of the textbook examples of taxa thought to be unable to disperse overwater, leading to what used to be called “disharmonic faunas”–islands that are missing some elements normally found on the mainland.
Detailed analysis indicates that the specimen is a member of the Plethodontidae, the family to which all neotropical salamanders belong. How did it get to Hispaniola? One possibility is that it hopped onto the proto-Antillean landmass as it passed by and perhaps came into contact with the continental Americas around 70 million years ago. Some hold that anoles got to the islands in the same way, though molecular data suggest that anoles are too young for vicariance to explain their occurrence in the Caribbean. The alternative possibility is that salamanders got to islands the old-fashioned way, by floating on flotsam and jetsam. Sensitive to dessication, most amphibians–and plethodontids in particular–wouldn’t seem good candidates for overwater dispersal, but stranger things have happened.
Regardless of how they got there, the presence of salamanders in the Caribbean twenty million years ago is a surprising finding adding a new dimension to our understanding of Caribbean biogeography.