Intraspecific Interaction and Mechanisms of Population Regulation in Experimentally Limited Habitat

Many populations of organisms deplete their resources, causing population growth rates to decline as population density increases. I used the sawtoothed grain beetle, Oryzaephilus surinamensis (L.), as a model to gain insight into the mechanisms of population regulation. Eight experiments differentiated the effects of crowding and food depletion on dispersal, mortality, and reproduction. Generally, food depletion caused increased mortality of immature beetles, sharply reduced oviposition, and increased adult dispersal. Rates of birth and death were both negative exponential functions of increasing density. The experiments quantify the trade-off between food and area in population regulation. These trade-offs variedwith initial abundance of larvae and adults and show the risk of ignoring abundances of any life stageswhen characterizing vital rates. I contrast population regulation of O. surinamensis with Tribolium sp., and suggest O. surinamensis is a good alternative for experiments on population dynamics because of better mobility and shorter development time.