Intransitive Eco-Evolutionary Feedback Loops Maintain Coexistence

AbstractThe maintenance of diversity has long been understood through the lens of the pairwise competitive interaction. However, work on the simplest multi- (three-)species systems have helped both evolutionary biologists and ecologists uncover mechanisms that maintain complex communities across both ecology and evolution. Rock-paper-scissors (RPS) dynamics illustrate how negative frequency dependence can affect evolutionary relationships and promote genetic diversity within populations. These same effects underlie the diversity of intransitive systems, which allow for the coexistence of even highly dissimilar competitor species. While these foundational diversifying mechanisms are common to both ecology and evolution, few studies have explicitly explored the potential role of simultaneous ecological and evolutionary intransitive loops as a powerful stabilizing and diversifying mechanism. In this synthesis, we examine the parallels between RPS dynamics and intransitive competition and how these common theoretical underpinnings point to the existence of intransitive eco-evolutionary feedback loops. Based on our synthesis of recent work, we propose that both intra- and interspecific intransitivity are working simultaneously to diversify natural communities, which in turn increases the probability of intransitive loops that further amplify and stabilize biodiversity across ecological scales. We provide conceptual support for the link between ecological and evolutionary intransitivity with a model simulation, which suggests that intraspecific intransitivity within a population can lead to greater levels of intransitivity at the community level, with direct implications for community diversity and stability.