Symposium: “Evolution in a community context: trait responses to multiple species interactions”
Casey P. terHorst, Peter C. Zee, Katy D. Heath, Thomas E. Miller, Abigail I. Pastore, Swati Patel, Sebastian J. Schreiber, Michael J. Wade, and Matthew R. Walsh (Mar 2018)
The DOI is https://dx.doi.org/10.1086/695835
Evolution in a community context limits adaptation to any single species, but results in adaptation to communities
Imagine if somebody tried to describe your personality based only on your interactions with one person. It would be nearly impossible because you interact with many different people, each in a different way. Moreover, you might interact with your parent differently when your partner is present, or when your whole family is present. Much of our mechanistic understanding of how species evolve is based on controlled observations and experiments involving one species evolving in response to one another. Yet, species live in a world of complex interactions with many other species: predators, prey, competitors, herbivores, pollinators, and many more. To understand how species evolve in natural environments, we need to better understand how evolution in response to many species differs from evolution in response to just one other species. A recent review by Casey terHorst of California State University, Northridge, and colleagues highlights a number of reasons why it is important to consider so-called “evolution in a community context”. “Evolution becomes more difficult to predict when we start thinking about many species,” terHorst says, “because we have to think about all the indirect ways that they interact with each other.” Imagine trying to play rock-paper-scissors; there is no winning strategy. It gets even more complicated if you use a version popularized on The Big Bang Theory: rock-paper-scissor-lizard-Spock. We have to think about how genes are linked. For example, natural selection might favor plants with versions of genes that make flowers with more nectar, but that gene may be negatively linked to another one that produces chemicals to defend against herbivores and another that affects competitive ability. As terHorst says, “It’s certainly not simple to think about, but we’re starting with baby steps to understand what happens with just a little more complexity, with the hope of building up to more complex models.”
Species that coexist in diverse natural communities interact in complex ways that alter each other’s abundances and affect selection on each other’s traits. Consequently, predicting trait evolution in natural communities may require understanding ecological and evolutionary dynamics involving a number of species. In August 2016, the American Society of Naturalists sponsored a symposium to explore evolution in a community context, focusing on microevolutionary processes. Here we provide an introduction to our perspectives on this topic by defining the context and describing some examples of when and how microevolutionary responses to multiple species may differ from evolution in isolation or in two-species communities. We find that indirect ecological and evolutionary effects can result in non-additive selection and evolution that cannot be predicted from pairwise interactions. Genetic correlations of ecological traits in one species can alter trait evolution and adaptation, as well as the abundances of other species. In general, evolution in multispecies communities can change ecological interactions, which then feed back to future evolutionary changes in ways that depend on these indirect effects. We suggest avenues for future research in this field, including determining the circumstances under which pairwise evolution does not adequately describe evolutionary trajectories.