Ecological changes in recent land-bridge islands in French Guiana, with emphasis on vertebrate communities

Abstract

In 1993 a multidisciplinary project investigating the effects of tropical rainforest fragmentation on land-bridge islands created by a hydroelectric reservoir was initiated in French Guiana (the Saint Eugène Fragmentation Project, SEFP). The main focus of the study is documenting changes in vertebrate groups, including lizards, birds, non-flying small mammals, bats and primates, that have marked differences in dispersal capacities. Here we summarize results of the first 4 years of research on SEFP (1 year pre-fragmentation, 3 years post-fragmentation), comparing islands with nearby control plots in continuous forest. Our results suggest that forest fragmentation has rapidly modified vertebrate diversity, regardless of the ability of species to disperse over water. Species present on islands do not represent a random sample of those present before isolation. Rather, a common suite of species has rapidly become dominant on each island, and these species share the following ecological traits: (1) they exhibit some of the largest body sizes in their guild, (2) they are generalists in habitat and food requirements, (3) they are naturally abundant in undisturbed forests, and (4) they have a wide geographic range yet are restricted to tropical rainforest. These results are interpreted in light of other studies of rainforest fragmentation.