Coexistence in a fluctuating environment by the effect of relative nonlinearity A minimal model

[摘要] The minimal model of the relative nonlinearity type fluctuation-maintained coexistence is investigated The competing populations are affected by an environmental white noise With quadratic density dependence the long-term growth rates of the populations are determined by the average and the variance of the (fluctuating) total density At most two species can coexist on these two regulating variables competitive exclusion would ensue in a constant environment A numerical study of the expected time until extinction of any of the two species reveals that the criterion of mutual invasibility predicts the parameter range of long-term coexistence correctly in the limit of zero extinction threshold However any extinction threshold consistent with a realistic population size will allow only short-term coexistence Therefore our simulations question the biological relevance of mutual invasibility as a sufficient condition of coexistence for large density fluctuations We calculate the average and the variance of the fluctuating density of the coexisting populations analytically via the moment-closure approximation the results are reasonably close to the simulated behavior Based on this treatment robustness of coexistence is studied in the limit of infinite population size We interpret the results of this analysis in the context of necessity of niche segregation with respect to the regulating variables using a framework theory published earlier (C) 2010 Elsevier Ltd All rights reserved

[发布日期] 2010-12-21

[关键词] Niche;Limiting similarity;Stochastic population dynamics