Abstract
Growing evidence shows that increasing global temperature causes population declines and latitudinal shifts in geographical distribution for plants living near their thermal limits. Yet, even populations living well within established thermal limits of a species may suffer as the frequency and intensity of warming events increase with climate change. Adaptive response to this stress at the population level depends on the presence of genetic variation in thermal tolerance in the populations in question, yet few data exist to evaluate this. In this study, we examined the immediate effects of a moderate warming event of 4.5°C lasting 5 weeks and the legacy effects after a 5 week recovery on different genotypes of the marine plant Zostera marina (eelgrass). We conducted the experiment in Bodega Bay, CA USA, where average summer water temperatures are 14–15°C, but extended warming periods of 17–18°C occur episodically. Experimental warming increased shoot production by 14% compared to controls held at ambient temperature. However, after returning temperature to ambient levels, we found strongly negative, delayed effects of warming on production: shoot production declined by 27% and total biomass decreased by 50% relative to individuals that had not been warmed. While all genotypes’ production decreased in the recovery phase, genotypes that grew the most rapidly under benign thermal conditions (control) were the most susceptible to the detrimental effects of warming. This suggests a potential tradeoff in relative performance at normal vs. elevated temperatures. Modest short-term increases in water temperature have potentially prolonged negative effects within the species’ thermal envelope, but genetic variation within these populations may allow for population persistence and adaptation. Further, intraspecific variation in phenology can result in maintenance of population diversity and lead to enhanced production in diverse stands given sufficient frequency of warming or other stress events.
Highlights
Over the century, mean temperatures are expected to increase [1]; increased temperature variability is likely to result in a more frequent short-term, extreme warming events [2,3]
Incorporating populations that live in environments distant from their thermal limits into climate change studies is rare
Individuals of the pasture grass, Anthoxanthum odoratuum, were more likely to survive aphid infestation if surrounded by unrelated individuals [15]. Still another possibility is that phenotypic plasticity may play an important role in population resilience
Summary
Mean temperatures are expected to increase [1]; increased temperature variability is likely to result in a more frequent short-term, extreme warming events [2,3]. Individuals of the pasture grass, Anthoxanthum odoratuum, were more likely to survive aphid infestation if surrounded by unrelated individuals [15]. Still another possibility is that phenotypic plasticity (or acclimation) may play an important role in population resilience. Plants that either exhibit tolerance to stressful environmental conditions or induce changes in morphology or physiology that allow them to maintain high fitness should be more likely than other individuals to persist as stressors increase [16,17]
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