Predation ofApochthonius minimus (Pseudoscorpionida: Chthoniidae) onFolsomia Candida (Collembola: Isotomidae) II. Effects of predation on prey populations

Summary

This study utilized the preference the pseudoscorpion,A. minimus, displays for certain sizes of the springtail,F. candida, in order to assess the population consequences of this selective predation. Although predation drove half of the treated collembolan populations to extinction, the populations which survived were not reduced in size and were in fact larger than most of the control populations (Figs. 1 and 2). During the first two weeks of the experiment, the predators apparently fed mainly on the original adults and the larger individuals of the second generation, thus increasing available space and improving the prey’s chances for successful reproduction. The resulting demographic shift accounts for the significant decrease in mean length that occurred in the experimental populations without any accompanying significant change in their total numbers. Some effects of density, food, and age-structure on the fecundity ofF. candida, acting in concert with the effects of size-selective predation, may lead to a variety of population consequences. In some circumstances, predation may cause increased production with decreased mean size, and no drastic change in standing crop. In different circumstances, a local population may become extinct. These results should further our understanding of the sporadic record of establishment and growth displayed byspringtail populations in the small, moist litter patches where they tend to aggregate.