The dynamics of collembolan populations: competitive relationships in an experimental system

Abstract

Three species of soil Collembola, Hypogastrura denticulata, Onychiurus armatus, and Sinella caeca, were cultured in single-species and a series of two-species cultures. The work described is an investigation of the intra- and inter-specific competitive interactions between these species. The populations were subdivided into five size classes and censused photographically every 2 weeks for 6 months. A factorial experimental design was used, consisting of two temperature regimes (a high fluctuating temperature and a constant 16 °C temperature) and 12 combinations of relative frequency of the species involved. Each treatment was replicated four times. Sinella proved to be the dominant species under the high fluctuating temperature conditions. Hypogastrura performed very poorly under these conditions, but was more successful in the constant 16 °C environment. Onychiurus did very well in single-species cultures in both environments, but declined in the presence of a second species. Coexistence was only obtained in some of the replicates from the 16 °C regime. In the interaction between Sinella and Hypogastrura the ultimate dominance was dependent upon the initial ratio of the two species. The mechanisms involved in these interactions are discussed.