Spatial and temporal analysis of α, β and γ diversities of bats in a fragmented landscape

We test a strategy for analyzing species richness in a landscape. This strategy is based on the joint analysis of alpha (local), beta (turnover) and gamma (landscape) diversities. We assessed the spatial and temporal relations among alpha, beta and gamma diversity of bats (Phyllostomidae and Mormoopidae) in a tropical landscape. In a spatial dimension, gamma diversity depends on the alpha diversity of the most species-rich community. The value of spatial beta diversity between habitats was very low. A high alpha diversity was found in a cornfield, which may be attributed to the reduced extent of the field (compared with a more extensive field) that allows the arrival of individuals from nearby rich communities. In a temporal dimension, within habitat cumulative richness over sampling period may be considerably different from the average richness. These differences are attributed to temporal turnover during short time intervals. Therefore, cumulative richness may be viewed as the temporal equivalent of within-habitat gamma diversity, which results of both average alpha and temporal turnover. We discuss, which value must be taken as an estimate of habitat species richness, the average or the cumulative alpha, and the implications that this decision can have in the evaluation of biodiversity.