Biogeography of Insular Biotas:


Another branch of our research concerns factors affecting the biogeography of insular populations and communities. Although important differences exist, empirical research on both real islands and habitat islands is relevant to management of landscapes fragmented by human activities.


Our field programs in the montane forests of northern Venezuela and in Costa Rica focus on studying faunas of habitat islands.  However, within each of these systems, the degree of isolation varies among habitat islands and among species.  Currently, we are using niche models to estimate the suitable areas of each species, allowing us to quantify their level of isolation.  These models then provide hypotheses regarding past connectivity, which we are testing with genetic data and in trait-based studies of community composition.  The work in Venezuela is in collaboration with José Ochoa-G. and Marisol Aguilera (see Anderson et al. 2012 for an overview of biogeographic patterns in the region).  Mariano Soley-Guardia has led the project in Costa Rica.

Map of the archipelago of Bocas del Toro, with an insert map showing its position within Panama; modified from Anderson and Handley, 2001 

Rob Anderson has also studied real islands, focusing on dwarfism and speciation in three-toed sloths of the landbridge islands of Bocas del Toro, Panama, which were formed in the past 10,000 years by rising sea levels (Anderson and Handley 2001, 2002).  He is collaborating with Nadia Barros and Link Olson (University of Alaska), who are sequencing DNA to elucidate molecular patterns of diversification. Because excellent collections of mammals from this region exist at the Smithsonian Institution, the islands and mainland of Bocas del Toro represent a superb study system for integrated tests of evolutionary and community ecology theory in an insular fauna for future studies with a multi-species perspective.

Map of northern Falcón, Venezuela, showing the Istmo de los Médanos, which connects the Península de Paraguaná to the "mainland."  Note the Serranía de San Luis (the east-west mountain range in the south) and the Cerro Santa Ana (the tiny, circular mountain on the Península de Paraguaná (see Anderson et al., 2012).