Spatial patterns of biological diversity in a neotropical lowland savanna of northeastern Bolivia

摘要

Understanding large-scale patterns of beta- and alpha diversity is essential for ecoregional conservation planning. Using the 110,000 km2 shallow basin of the Beni savannas of northeastern Bolivia, we examined the spatial patterns of biological diversity of four taxonomic groups (bats, palms, reptiles, and amphibians). Since the Beni savannas are shaped by cycles of drought and flood, and farming, which, together with topography, create a mosaic of sub-ecoregions from Amazonian forests to aquatic vegetation, we hypothesize that this landscape heterogeneity results in a high turnover in species composition across sub-ecoregions. We compiled species lists for each taxon and modeled the potential distribution of each species using the algorithm MaxEnt. For those species whose modeled potential distribution produced incongruous results, we built presence-absence maps. Using the potential distribution maps, we estimated the lists of species for each sub-ecoregion. In order to establish present similarities in species composition between sub-ecoregions, we constructed dendrograms using cluster analysis of presence-absence matrices. The sub-ecoregions associated with the Moxos (southern part of the Beni savannas) were richer than the sub-ecoregions composing the Beni Cerrado (northern part of the Beni savannas). Centers of species richness were detected in the savanna-type sub-ecoregions (bats and reptiles) or associated with the Várzea forests (palms and amphibians). A south-north gradient in the pattern of distribution of four taxonomic groups was also recorded. The results suggest that the patterns of biological diversity partially respond to the mosaic arrangement of the landscape. Future exercises on conservation planning will point to total target areas about 5,000 km². This area seems to be sufficient to contain the biological richness of the region at least for the taxa analyzed.