HATCH DENSITY VARIATION OF A GENERALIST ARTHROPOD PREDATOR - POPULATION CONSEQUENCES AND COMMUNITY IMPACT

We examined density dependence in population attributes and community impact of a generalist predator by experimentally mimicking natural va riation in initial cohort densities produced by synchronous egg hatch in Mantis religiosa (Mantodea: Mantidae). Mantid cohorts within the no rmal range of emergence from a single egg mass were established in a r eplicated, well-controlled open held experiment. On the scale of the p rogeny from a single female, density-dependent food limitation caused mortality and ontogenetic asynchrony to increase with increasing densi ty. All cohorts converged to a common level of abundance and biomass b ecause both development rate and population size declined with increas ing initial density. Numbers and biomass of other arthropods generally declined with increasing initial density of mantids, although there w ere both positive and negative effects on different taxa. The abundanc e of hemipterans (almost exclusively herbivorous mirids) increased in the presence of mantids; this was an indirect effect as large in magni tude as any of the direct reductions in abundance of other taxa. Per c apita interaction strengths of mantids on most taxa generally were wea k except for the strong positive interaction with hemipterans. In spit e of different mantid development rates among treatments, predator loa d (proportion of arthropod biomass present as predators) for all three treatments, attributable mainly to mantid biomass, converged to appro ximately five times control level by the end of the experiment. The di fferences in predator loads between control and treatment plots thus m ay represent different levels of predator saturation: one for control plots, where predator load was constant over time and in which general ists contributed relatively little to predator biomass, and a higher o ne for treatment plots, in which generalists comprised the bulk of pre dator biomass. Predator load may therefore be an indicator of the rela tive importance of generalist vs. specialist predators in terrestrial arthropod assemblages.