Climate change triggers morphological and life-history evolution in response to predators

Background/Question/Methods

Although climate change is expected to reorganize entire communities, this restructuring might reflect either ecological or evolutionary responses directly to abiotic conditions or indirectly mediated through altered species interactions. We tested the hypothesis that changes in trophic interaction strength due to altered predator abundance have a cascading evolutionary response in a prey species (Daphnia pulex). Using a multiyear / multigenerational field experiment we manipulated a dozen open aquatic mesocosms to simulate hydrological conditions under climate change.  At the end of our three-year press experiment, we collected Daphnia pulexfrom each pond and raised them in a common garden.  Using standard quantitative genetic methods, we measured a series of quantitative traits every other day on 108 (4 treatment levels * 3 replicates / level * 3 clonal lines / replicate * 3 clones / clonal line) individuals for eight weeks.  With these data, we used structural equation modeling and model selection to test for causal relationships between traits, abiotic treatment variables and biotic covartiates.

Results/Conclusions

We found a significant decrease in tail spine length and population growth rate in groups exposed to the most extreme future climate scenarios.  Our structural equation models demonstrated that trait changes were best explained as an indirect effect of our treatment mediated through changes in predator abundance.

Our results suggest climate change can trigger a cascade of ecological and evolutionary forces by reducing predator density, which in turn acts as a selective force leading to evolutionary change in prey morphology and life history.  This represents a significant empirical demonstration of the importance of eco-evolutionary concepts that have gained much traction in the recent literature surrounding climate change.