How do body size and habitat fragmentation influence extinction in lizards? A long-term case study on artificial islands in the Brazilian Cerrado

Habitat fragmentation is known to cause extinctions and species turnover, but the factors that allow some species to persist while others become locally extinct are not well understood. Landscape flooding following the construction of hydroelectric dams causes a particularly dramatic form of fragmentation disturbance, where former terrestrial habitats become aquatic and former hilltops become land-bridge islands. As such, reservoir land-bridge islands have become a successful model for accessing the impacts of fragmentation on biodiversity. We used the lizard community, to assess species sensitivity to habitat structural change during land-bridge island formation. We monitored the lizard community for 23 years before, during, and after the flooding of the Serra da Mesa Dam reservoir. Over the course of our study, the diversity of the lizard community on land-bridge islands and mainland sites along the shores of the newly formed reservoir declined from 19 to six species. We found that in Serra da Mesa islands, lizards with large body sizes (e.g., Teiidae and Tropiduridae) decreased in abundance along the flooding process, thereby increasing their extinction risk. In contrast, we found a high abundance of small-bodied lizards (Gekkonidae, Gymnophthalmidae, Scincidae, and Sphaerodactylidae) on Serra da Mesa islands. Richness on the islands declined dramatically, resulting in communities currently with one highly abundant species, Gymnodactylus amarali. For the sake of biodiversity conservation, island or fragment sizes must be considered for maintaining a reasonable number of species and our characterization of the local extinction patterns may provide relevant information to mitigate wildlife depletion due to habitat fragmentation.