Fauna de opiliões da reserva Ducke, com ênfase no ajuste de métodos de coleta

Abstract

Harvestmen (Arachnida, Opiliones) sampling studies, for taxonomical and ecological purposes, are scant. Harvestmen have been collected with methods developed for spiders, which may be redundant and not very effective for obtaining taxonomical and ecological information about the community. With the objective of reducing the sampling effort, four collecting methods (maximum effort) were tested in a 2.500ha area of upland dense ombrophilous amazon forest. The harvestmen were collected in 30 plots of 250 x 2 m distributed at 1km intervals. Three variations of active night collecting and a beating sheet were used in four subplots of 30 x 10 m in each plot. Among the variations there were two new methods tested, modified active night collecting and cryptic active night collecting, which consisted of 1h searches throughout the cryptic habitats of the whole plot. A total of 2.338 individuals, in 23 taxa, 16 genera and 10 families, were recorded. The beating sheet sampled only one species. The cryptic active night collecting sampled all taxa collected through the maximum effort. Principal Coordinate Analysis (PCoA) detected congruency between the collecting methods. Redundancy Analysis (RDA) detected that the variables that influenced the harvestmen community were the number of palm trees and leaf litter depth. The active night collecting, and the cryptic variation, access the same ecological patterns obtained by the three collecting methods on number of palm trees, leaf litter depth and soil humidity. Besides an increase on the number of sampled species, the cryptic active night collecting also resulted in the same ecological patterns observed with the maximum effort. Furthermore, sampling time, identifications and financial costs were reduced around 87% when compared to the maximum effort. In conclusion, cryptic active night collecting is the best method for dense ombrophilous amazon forests.