competitive abilities in experimental microcosms are accurately predicted by a demographic index for r微观竞争能力在实验准确地预测人口指数r.pdfVIP

Competitive Abilities in Experimental Microcosms Are Accurately Predicted by a Demographic Index for R* 1 2 Ebony G. Murrell *, Steven A. Juliano 1 Department of Entomology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America, 2 School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America Abstract Resource competition theory predicts that R*, the equilibrium resource amount yielding zero growth of a consumer population, should predict species’ competitive abilities for that resource. This concept has been supported for unicellular organisms, but has not been well-tested for metazoans, probably due to the difficulty of raising experimental populations to equilibrium and measuring population growth rates for species with long or complex life cycles. We developed an index (Rindex) of R* based on demography of one insect cohort, growing from egg to adult in a non-equilibrium setting, and tested whether Rindex yielded accurate predictions of competitive abilities using mosquitoes as a model system. We estimated finite rate of increase (l9) from demographic data for cohorts of three mosquito species raised with different detritus amounts, and estimated each species’ Rindex using nonlinear regressions of l9 vs. initial detritus amount. All three species’ Rindex differed significantly, and accurately predicted competitive hierarchy of the species determined in simultaneous pairwise competition experiments. Our Rindex could provide estimates and rigorous statistical comparisons of competitive ability for organisms for which typical chemostat methods and equilibrium population conditions are impractical. Citation: Murrell EG, Juliano SA (2012) Competitive Abilities in Experimental Microcosms Are Accurately Pred