Invasion Consequences in Communities Maintained by Niche and Intransitive Coexistence Mechanisms.

Understanding invasion mechanisms or identifying their potential outcomes has been a longstanding objective of invasion. Many recent empirical and theoretical works tend to frame a perspective of invasion biology within the field of coexistence theory. With increasing emphasis on indirect competitions, more researches hold that niche departure, intransitive loop structure or the integration of these two would be the potential mechanisms to promote native coexistence. But how invasion dynamics rely on these key properties of native competitive network is seldom investigated. Here, we introduce one alien species to a three-species competition system. By setting the structure of coexistence coefficient matrix, we consider three native coexistence mechanisms. After analyzing the equilibrium consequences of alien species invasion under these three mechanisms, we have found that (1) in the native communities supported by strong niche differentiation, alien species can certainly establish their population but would not pose great destruction to native species. (2) Invasion exclusion would happen in the community maintained by intransitive competition loop. However, whether alien species coexist with or exclude resident populations depends on both intraspecific and interspecific competition of invader. (3) The community assembled by the combination of these two mechanisms are most resistant to invasion, and where invasion consequences are more diverse. (4) Finally, the species long-term steady state and short-term respond always keep consistent. We have explicitly situated invasion process within the recent coexistence framework. Our results would broaden the understanding of invasion mechanisms and provide insights into the combination of invasion and coexistence theory. [ABSTRACT FROM AUTHOR]