Effects of sampling intensity on the collection of spider (Araneae) species and the estimation of species richness

In this study I compare the relative effectiveness of temporally and spatially constrained sampling strategies on the collection of spiders, and discuss how the sampling strategy used may affect estimates of spider species richness. Using 3 time-based collecting methods (ground sampling, above ground sampling, and vegetation beating) and 1 area-based method (Tullgren leaf litter extraction), 3 collectors sampled spiders from 10- by 50-m plots in a cove forest in the Ellicott Rock Wilderness Area of northern Georgia between 18 May and 4 June 1993. Eighty samples collected from four 10- by 50-m plots (0.2 ha) contained 77 species, and 77 samples from 24 such plots (1.2 ha) contained 78 species. A total of 2,842 adults spiders was collected from the 1.4 ha sampled, representing 92 species, 64 genera, and 20 families. Increasing the collecting effort per unit area (repetitive collecting) is a more efficient strategy for collecting cryptic or covert species as opposed to spreading the sampling effort over a larger area (nonrepetitive collecting). It is suggested that before arthropod assemblages are included in management decisions, the methods used to collect the species must by fully examined. Richness estimates for the site ranged from 85 to 144 species using the repetitive strategy, from 88 to 95 for the nonrepetitive strategy, and from 102 to 112 for the entire dataset.