Geographic distance and the role of island area and habitat diversity in the species-area relationships of four Lesser Antillean faunal groups: a complementary note to Ricklefs & Lovette

1. Recently, Ricklefs & Lovette (1999) have emphasized the possible confounding effect of habitat diversity on area while studying species-area relationships. They illustrated this problem using four groups of organisms (birds, bats, herptiles, and butterflies) on 19 islands of the Lesser Antilles. Although they referred to the potential for species to migrate between islands, they did not take into account the geographical distances between islands. 2. Here, I reanalyse their data using a multivariate method, based on permutation of distance matrices, which incorporates pairwise geographical distances between islands. The analysis includes as independent variables the geographical distances between pairs of islands, size, maximum elevation, and habitat diversity of each island. The last three variables were obtained from Ricklefs & Lovette (1999). 3. Results of the analysis were similar to those of Ricklefs & Lovette (1999). In addition, however, geographical distances influenced species richness of bats, birds and butterflies. 4. These new results are helpful for investigating the processes that may contribute to the observed pattern of species richness. The level of endemism of the four taxonomic groups is related to the influences of geographical distances among islands, and might be explained by differences in their vagility. 5. Finally, I emphasize the need to incorporate geographical distances among islands, using statistical methods that can manipulate distance matrices.