Evolutionary responses to environmental change: how do trophic interactions affect adaptation and persistence?

Background/Question/Methods

It is imperative that we understand joint ecological and evolutionary responses to climate change to predict future threats to biological diversity. According to recent reviews, how trophic interactions may affect evolutionary responses to climate change remains unanswered. Here we explore the eco-evolutionary dynamics of a plant species with and without a herbivore species in a warming environment. We do this in a semi-realistic setting with species growth and interactions determined by thermal and plant-herbivore interaction traits. We consider evolution to occur in a two phase process: (co)evolution without warming followed by (co)evolution with warming. We hypothesize that trophic interactions change population densities, which, indirectly affect adaptation and persistence through altering rates of trait change, ultimately leading to reduced adaptation rate and persistence time of the plant species.

Results/Conclusions

Through our modeling, we have achieved a better understanding of the important eco-evolutionary channels through which trophic interactions may act and quantified likely scenarios in a warming environment. Overall, the addition of a herbivore affects plant population size, strength and direction of selection, and the evolutionary attractor. The herbivore reduces adaptation speed and persistence time of the plant by reducing density, but can also act through other mechanisms: the herbivore can create other coevolutionary attractors where thermal traits do not always match the temperature of environment. These coevolutionary attractors can be predicted by relative thermal niche widths and create different targets and trajectories in a warming environment. Intermediate plant thermal niche width generally leads to low persistence time of the plant with and without the herbivore in a warming environment. This study shows that it is necessary to know how the contrasting mechanisms (population size, strength of selection, "roadblocking" in trait space, evolutionary attractors), play out for trophic interactions in a food chain in order to make even simple predictions for species faced with climate change.