Summers are very quiet in the Hadly lab, because everyone is out in the field. This summer, my research on extinction and diversification in insular lizard communities took me to the French Caribbean. I spent eight days on Grande Terre and La Desirade, catching lizards, hiking, learning French, and outsmarting tropical storms with two undergraduate research assistants in tow. Our mission was to evaluate the islands for future paleontological work. These islands were chosen because little fieldwork has been done previously, and unlike many island in the Caribbean, they are largely limestone in composition, providing the necessary substrate for fossilization in caves and fissures.
Saint Francois served as our port of entry into La Desirade, a small island off the coast of Grand Terre. Unless you have your own private plane or boat, you have to take the morning ferry to get to La Desirade. During the Late Pleistocene, we could have made the journey by foot, because these two islands, along with Basse Terre, are part of a larger island bank that was exposed during the Last Glacial Maximum. Many islands in the Lesser Antilles are connected in this manner, and as an island biogeographer, I am interested in the ramifications of island fragmentation on faunal assemblages.
The ferry companies each make one roundtrip every day to this former leper colony. We used one of our two days on Saint Francois to visit the surrounding areas, including Pointe du Vent, which was excavated previously (Pregill et al. 1994). The area has since been developed into a residential community, so our paleontological prospects were minute, but we seized the opportunity to survey the lizard fauna. As expected, Guadeloupe’s endemic anole, Anolis marmoratus was prevalent, but we also found the gecko Sphaerodactylus fantasticus in leaf litter.
La Desirade was full of surprises. On the uninhabited Eastern and Western ends of the Route Principale, we found the endangered Iguana delicatissima, which is endemic to the Lesser Antilles. With a historical range extending from Anguilla to Martinique, Iguana delicatissima has been extirpated from many of these islands due to hunting, predation by introduced species, and habitat loss. Interbreeding with the introduced green Iguana (Iguana iguana) poses an additional threat to the genetic integrity of this majestic lizard.
The fauna of La Desirade are rivaled only by the island’s geology. The basement rock from the island is the oldest geological unit of the Lesser Antillean island arc (Cordey and Cornée 2009), and originated in the Pacific ocean (Baumgartner et al. 2004). On top of these units are Quaternary limestones, the rock of interest to us. La Desirade, like the rest of the Lesser Antilles, is geologically heterogeneous and extremely complex. It is this complexity that makes the system appeal to me.
I was truly impressed by the beauty of this system, and I look forward to future fieldwork here, including excavating some units that we found. These data will be integral in understanding the history of diversification and extinction not only on the Guadeloupe Bank, but in the Lesser Antilles as a whole. As island area continues to change due to sea-level rise, faunal assemblages will continue to change, and insight from past events can assist us in understanding the evolutionary trajectory for extant and future populations.
BAUMGARTNER P.O., BANDINI A. & DENYER P. (2004). Jurassic-Lower Cretaceous radiolarites in Central America and the Caribbean – remnants of Pacific ocean floor. Second Swiss Geosc. MeetingAbs., Lausanne, 1-2.
Breuil, M., Day, M. & Knapp, C. (2010). Iguana delicatissima. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. <www.iucnredlist.org>. Downloaded on 11 September 2012.
Pregill, G. K., D. W. Steadman, and D. R. Watters. (1994). Late Quaternary vertebrate faunas of the Lesser Antilles: Historical components of Caribbean biogeography. Bulletin of Carnegie Museum of Natural History No. 30.
Photos courtesy of M. Kemp (firstname.lastname@example.org) and S. Scarpetta