Establishing reliable spider (Araneae, Araneidae and Thomisidae) assemblage sampling protocols:: estimation of species richness, seasonal coverage and contribution of juvenile data to species richness and composition

The capacity of short-term sampling to provide reliable estimates of annual spider assemblages (Araneidae and Thomisidae) present in a Mediterranean site was analyzed, along with the contribution of juvenile data on estimations of spider species richness. A Standardized year-long sampling protocol in a one-square-kilometer plot in central Spain yielded reliable Araneidae and Thomisidae inventories. To compare sampling design efficiencies, the degree of completeness of collected annual inventories was estimated, along with an "optimal sampling" selection of months, i.e. the minimum number of months indicating most accurately the number of species present throughout the year. The completeness of spring-month sampling, as well as that of every month, was also estimated. Calculations both included and excluded immature stages. When multiple localities must be sampled and fieldwork minimized, a 1-month spring sampling protocol reasonably estimates the entire spring fauna, allowing effective comparisons between sites during the richest period. Our results indicate that juveniles must be included in the sample in order to obtain reliable estimates of species richness, and they should be stored apart from adults in order to analyze them separately as advances in their identification are achieved.(c) 2006 Elsevier SAS. All rights reserved.