Comparison of endogeic and cave communities: microarthropod density and mite species richness

Quantitative studies of mite communities in endogeic and cave ecosystems are scarce. In this paper, we tested and validated the hypotheses that (1) deep soil and cave mite communities are distinct and (2) that species composition is more variable in caves than in deep soils. Mites were sampled in May, November, and January at 15–20 cm depth in three temperate forest soils and at the surface of sediments in two caves situated directly below two of these soils. Endogeic mite densities ranged from 77 to 225 individuals/dm3 vs. 9 to 43 in caves. Organic matter was found to be the main factor correlated to density in soils while flooding are thought to profoundly affect cave communities: it introduce accidental species that eventually die without breeding, inducing a sharp seasonal variation in mite density. Mite richness estimates amounted to about 80 species in most locations. (1) Cave populations were distinct from endogeic ones and migration between those habitat compartments is thus supposed to be infrequent. (2) Both the fragmented structure and flooding that lead to the addition of accidental species, are invoked to explain the larger variability of cave communities compared to soil communities.