Landscape connectivity may explain anuran species distribution in an Atlantic forest fragmented area

Abstract

In this work we evaluated anuran species distribution in an Atlantic forest fragmented landscape, in the state of Rio de Janeiro, Brazil. Sampling was carried out in three continuous forest sites, 12 forest fragments, and five pasture areas (matrix). We recorded, by visual encounter surveys, 2,495 individuals from 50 amphibian species for all sampled areas. Considering the pooled data, higher richness occurs in continuous forest area. Additionally, more than a third of species that occurred in continuous forest area did not occur in fragments or in matrix. Both ordination analyses showed that continuous forest sites clustered together and matrix areas seemed to be separated from other areas. This ordination resulted from the existence of species occurring only in continuous forest, suggesting that these species may be sensitive to habitat fragmentation. Besides, matrix appears separated from other areas due to occurrence of frog species typical from disturbed environments, which are not recorded in continuous forest sites or in sampled fragments. By analyzing the effect of landscape metrics, we found that there was a tendency for fragments with lower isolation to have higher species richness and proportion of species which did not occur in matrix areas and amphibian local communities seems to be affected in a more local scale by habitat changes. Because local matrix is apparently hostile to typically forest-associated amphibian species, many of them may be unable to reach most isolated fragments by dispersal, which may explain observed results.