Quantitative Characteristics of Stabilizing and Equalizing Mechanisms.

AbstractAn understanding of the mechanisms that facilitate coexistence in ecological communities poses a major challenge to theoretical ecology. A popular paradigmatic scheme distinguishes between two qualitatively different processes that help species to coexist: stabilizing mechanisms increase niche differentiation, making the intraspecific competition stronger than the interspecific one, while equalizing mechanisms diminish fitness differences, making the competition less decisive. Here, we provide an analytic and numeric examination of the quantitative features associated with this scheme for a simple, two-species competition model. We show that the main metrics of persistence change only slightly along the stabilizing-equalizing continuum, where niche overlap increases while fitness differences decreases. Therefore, persistence properties cannot indicate the dominant mechanism that promotes coexistence and vice versa. Cross correlations between abundance time series are shown to provide a decent characterization of the mechanisms that promote coexistence. The relevance of these insights to the analysis of diverse assemblages is discussed.