Patterns of Resource Use and Tests for Competitive Release in a Spider Community
1983
Riechert, Susan E. | Cady, Alan B.
Determinations were made of the temporal, functional (diet), and spatial niche relations of four web—building spider species comprising 98.3% of the individuals of a sandstone rock outcrop community. Three of the species were found to be potential ecological equivalents; despite dissimilar web structures, significant overlaps (60—85%) were exhibited in their diets, timing of activity, and microhabitat use. Investigation of the degree to which various resources were in limited supply to these species during the course of the study indicates that: (1) space was a potentially limiting factor, while (2) prey availability appeared to be in excess of the needs of the populations. We complete removal experiments to seek evidence for changes in various demographic parameters of the populations (i.e., in adult and juvenile densities and in egg production) and in use of various microhabitats in the absence of heterospecifics. No evidence for competitive release was observed on the single—species cliffs during the 11—mo period of the experiments. Data are presented that suggest interspecific effects present may be masked and/or offset by the operation of other impinging effects (e.g., [1] the fact that by removing all other spiders from the experimental cliffs, we were removing a major source of food to one of the species and [2] the presence of potentially limiting intraspecific competitive effects to three of the species populations).
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