Dispersal-mediated coexistence under recruitment limitation and displacement competition

Understanding biodiversity maintenance when species compete for shared limiting resources remains an outstanding ecological problem. For a half century, the competition–colonization trade-off has been invoked to explain species coexistence. More recently, asymmetric dispersal has been shown to alter the conditions for species coexistence under pure scramble competition for space, even in the absence of spatial heterogeneity. Therefore, in this study, we investigated why and how asymmetric dispersal may alter the effect of competition–colonization trade-off on species coexistence. Our main findings are that: (1) self-recruitment of a superior competitor facilitates persistence of an inferior competitor; (2) the degree to which a community is recruitment-limited influences the threshold dispersal asymmetry required for persistence of a species with a birth or survival disadvantage; (3) an inferior competitor with a high recruitment strategy is better able to benefit from spatial asymmetries in dispersal than one with a high survival strategy, and (4) an inferior competitor may persist, and even exclude the superior competitor, when dispersal is highly asymmetric (i.e., the competition–colonization trade-off can be violated). These results underscore the importance of dispersal patterns promoting species coexistence and their synergies with species’ colonization and competition abilities, and highlight the need to assess dispersal-mediated coexistence within a framework that incorporates the interactive effects of dispersal patterns, demographic and competitive strategies.