Competition between Two Unrelated Species of Soil Cryptostigmata (Acari) in Experimental Microcosms

SUMMARY (1) High density laboratory populations of Hermanniella granulata (Nic.) and Nothrus sylvestris (Nic.) were established in natural soil and litter microcosms under constant temperature and humidity conditions. (2) The two species in pure populations had overlapping niches with differences in sub-horizon and microhabitat occupation as well as food resource selection. (3) In mixed populations both species underwent significant niche shifts in their utilization of food and space: Hermanniella moved into the litter layers while the Nothrus population increased in the fermentation layer. A complex pattern of changes in microhabitat occupation and in the selection of major groups of food resources was also observed. (4) The time scale over which these changes occurred suggest an interference phenomenon between the two species but the precise mechanism is unknown. (5) This is the first time that competitive interactions of this type have been demonstrated between Cryptostigmata, or any other soil animals.