Composição e riqueza de espécies de anuros (Amphibia) em fragmentos florestais no Lago de Tucuruí, Pará

Abstract

Habitat loss and forest fragmentation represent serious risk to anuran species maintenance in Amazonian. Herein, we determine composition, richness and abundance of anuran species in forest fragments at two Zones of wildlife protection (ZWP) established at the Tucuruí dam, east Pará state. Anuran fauna was sampled through transects at twelve fragments of different sizes, distributed along the two ZWP, the first on the right (ZWP-R) and the second on the left (ZWP-L) edge of the lake. Frogs were registered through active search and pitfall trap captures. From January to July 2005 we registered 2370 individuals from 35 anuran species. Thirty species were found in the ZWP-L (13 exclusive species) and 22 in the ZWP-R (five exclusive species). Seven estimators of species richness were obtained with the use of EstimateS® Software. For the most estimators, curves of species accumulation trended to stability. However, estimates of species richness varied among the estimators, with bootstrap the lowest (38) and the Jacknife the highest (45) values. The combination of the species observed here with the nine species registered in the Herpetological Collection of the Museu Paraense Emílio Goeldi resulted in 44 species, suggesting that estimators for species richness had a reasonable performance. Similarity of anuran species was higher among fragments from the same edge of the lake than from similar size fragments. Species richness was positive and significantly related to size, but not to distance from the fragment from continuous forest. There was no significant relationship between number of individuals observed in the fragment and the fragment size. Differences in the species composition between the two ZWP suggest certain complementariety of the two unities to the conservation of the local anuran fauna, as well the need of a higher effort of anuran sampling, principally through the increase of study area, for the best comprehension of these differences and their implications.