Dear Dr. Thrall,

We are pleased to be submitting our Perspectives paper for the Ecology Letters special issue “Exploring the Border between Ecology and Evolution”. We were in correspondence with Dr. Hello and yourself in May and were invited to submit this manuscript. We thank you for your time and consideration.

Rock-paper-scissors dynamics have been shown to affect the evolutionary dynamics at play within species and populations and are analogous to the ways in which intransitive competition modifies competitive outcomes and the co-existence of species. While these processes are studied by both ecologists and evolutionary biologists in a growing body of literature, there is an absence of research into how these processes may be working simultaneously across both ecological and evolutionary scales. The continued separation of ecological and evolutionary research has led to an incomplete and fragmented understanding of both rock-paper-scissor dynamics and intransitive competition.

In our Perspectives article we explore the similarities between rock-paper-scissor dynamics and intransitive competition and how this link opens new avenues of research into eco-evolutionary processes. We begin by investigating how rock-paper-scissor dynamics and intransitive competition have each been used in past research to explore the diversity and stability of systems. In particular, intransitive dynamics have been shown to drive the stable coexistence of different phenotypes within species. At the same time, these dynamics clearly operate at the community level to maintain diversity across species. In doing so, we argue that this phenomenon (intransitivity) occurs simultaneously in both ecological and evolutionary contexts, and represents an exciting new avenue of research linking these disciplines. Our review of the literature highlights not only the presence of intransitive dynamics in both ecological and evolutionary contexts, but the potential existence of feedback mechanisms that operate between them. Using simulations adapted from Maynard et al. (2019), we provide mathematical support for the idea that greater intraspecific intransitivity between phenotypes within a population can lead to greater levels of intransitivity between species at the community-level, with direct implications for community diversity and stability.

Novelty of this work: This is the first paper that explicitly makes this connection, and we hope that our conceptual framework will strengthen our understanding of how non-hierarchical interactions shape both evolutionary and ecological outcomes. We provide promising directions for future research and our work creates a path towards an improved interpretation of natural systems that is more dynamic, integrative, and holistic.

We hope that you would consider this for possible publication in Ecology Letters. No part of this has been submitted elsewhere.

Yours sincerely,

Giacomo Delgado

Rock-Paper-Scissor Dynamics and Intransitive Competition link Ecology and Evolution

Giacomo L. Delgado (gidelgado@student.ethz.ch, ETH Zurich, Department of Environmental Sciences),

Daniel Maynard (dan.s.maynard@gmail.com, ETH Zurich, Department of Environmental Sciences),

Jukka Jokela (jokela@env.ethz.ch, ETH Zurich, Department of Environmental Sciences,

Thomas, W. Crowther (Tom.Crowther@usys.ethz.ch, ETH Zurich, Department of Environmental Sciences)