Spider Colonization of Agroecosystems: Mode and Source

The means by which spiders arrive in newly cultivated fields were investigated in east Tennessee study plots through collections of cursorial and aerial immigrants into a garden system; through experimental manipulations of garden plots to distinguish between aerial and cursorial immigrants; and through censuses of the spider faunas of garden plots and of neighboring habitats in various stages of succession. The familial compositions of the aerial dispersers and cursorial dispersers differed significantly. Further, the majority of the spiders entering the garden plots arrived via ballooning (passive dispersal on air currents). Mark-recapture experiment results indicate that bordering habitats can contribute spiders if these are physiognomically similar. However, ≍50% of the spider species found in our garden plots were not found in nearby “natural habitats.” This represents a minimum estimate of the contribution of long-distance immigration. These data indicate that spider immigration into agricultural systems is not dependent on a neighboring reservoir (natural habitat).