Consequences of local adaptation and plasticity in eelgrass response to ocean warming

Background/Question/Methods

Within species, the spatial distribution of phenotypic variation and its causes (i.e., local adaptation or plasticity) will determine species’ adaptive capacity to respond to a changing environment. However, little is known about the spatial scale of adaptive differentiation among populations or the temporal scale of sustained plastic response within populations. Here we will discuss the results of recent studies aimed at understanding the consequences of fine-scale local adaptation and long-term plasticity in eelgrass (Zostera marina) response to ocean warming.

Results/Conclusions

Coupling a year-long three-way reciprocal transplant experiment with a temperature common garden experiment we reveal how three eelgrass populations within a single estuary can be adapted to local temperature gradients. More specifically, we identified a range-center eelgrass population that is pre-adapted to extremely warm temperatures like those experienced by low-latitude range-edge populations of eelgrass, demonstrating how reservoirs of heat-tolerant phenotypes may already exist throughout a species range. In a separate study, we show how a simulated extreme warming event causes persistent changes in the morphology and growth eelgrass across multiple clonal generations and multiple years. Long-term increases in above to below ground biomass ratios could indicate an adaptive clonal transgenerational response to warmer climates that reduces the burden of increased respiration in belowground biomass. Together, results from both studies indicate that evolutionary mechanisms may greatly enhance eelgrass resilience to ocean warming and that predicting species resilience to global change should incorporate potential buffering effects of local-scale population differentiation and trans-generational plasticity.