The interaction between competition and predation: A meta-analysis of field experiments

Gurevitch, J Morrison, JA Hedges, LV

J. Gurevitch et al., The interaction between competition and predation: A meta-analysis of field experiments, AM NATURAL, 155(4), 2000, pp. 435-453

76

INGLESE

Article

Environment/Ecology

AMERICAN NATURALIST

0003-0147 → ACNP

155

4

2000

435 - 453

ISI

0003-0147(200004)155:4<435:TIBCAP>2.0.ZU;2-R

Ecologists working with a range of organisms and environments have carried out manipulative field experiments that enable us to ask questions about th e interaction between competition and predation (including herbivory) and a bout the relative strength of competition and predation in the field. Evalu ated together, such a collection of studies can offer insight into the impo rtance and function of these factors in nature. Using a new factorial metaa nalysis technique, we combined the results of 20 articles reporting on 39 p ublished field experiments to ask whether the presence of predators affects the intensity of competitive effects and to compare the average effects of competition and predation. Across all studies, the effects of competition in the presence of predators were less than in the absence of predators, an d the interaction between competition and predation for most response varia bles was statistically significant. Removal of competitors had much more po sitive effects on organisms' growth and mass than did exclusion of predator s. Predator exclusion had much more beneficial effects on organisms' surviv al than did competition. The mean effects of competition and predation on d ensity did not differ from one another. The results differed among trophic levels. Further understanding would benefit greatly from more field experim ents that manipulate both competition and predation, that focus on a wider range of organisms and environments, that focus on population-level paramet ers such as density, and that report results more completely, including dat a such as sample sizes and variances.