An empirical study linking behaviour and population dynamics: altering spatial food availability in a mite model system.

Abstract

Differences in the spatial availability of food can cause significant differences in the dynamics, age structure and size structure of a population. Replicated laboratory colonies of the soil mite Sancassania berlesei were fed the same absolute amount of food (yeast) daily, given either in a clumped form (or as a ball of yeast) or as a fine powder which was spread evenly. Animals were left to reproduce freely and population counts and measurements of animal length were taken every four days for 300 days. Animals in colonies fed clumped yeast have a higher initial oscillation in egg, juvenile and adult numbers than those fed a dispersed resource. In addition male and female lengths are larger in colonies fed clumped food, although the variance in length is also greater. Later in the time series adult numbers become similar between the two treatments, but the colonies fed clumped food maintained a roughly two-fold higher egg and juvenile number than colonies fed powder. The results are consistent with the idea that spatial arrangement of food can influence the type of competition acting at the individual level.