Eco-evolutionary context modifies a destructive plant invader's response to climate

Area of Science:

• Ecology
• Evolutionary Biology
• Plant Science

Background:

• Predicting plant population dynamics under climate change necessitates understanding climate-fitness relationships.
• The invasive annual grass Bromus tectorum (cheatgrass) is a model system for studying plant adaptation and ecological responses.

Purpose of the Study:

• To investigate how eco-evolutionary context mediates the relationship between climate and fitness in Bromus tectorum.
• To assess the role of local adaptation to climate in explaining fitness variation.
• To determine the influence of microclimate, planting density, and genotype-by-environment interactions on cheatgrass fitness.

Main Methods:

• A replicated common garden experiment was conducted over two years at four sites.
• 96 genotypes of Bromus tectorum were grown under manipulated soil microclimate conditions (varying surface albedo) and planting densities.
• Climate mismatch was calculated to assess local adaptation, and statistical models were used to predict fitness.

Main Results:

• Genotype-by-environment interactions improved the predictive accuracy of the fitness model, with strong evidence for local adaptation to source climate.
• Survival responses to soil microclimate were density-dependent.
• Local adaptation was more evident at lower planting densities compared to higher densities.
• The model generally predicts increased fitness with rising temperatures across source populations.

Conclusions:

• Eco-evolutionary context, including genotype-by-environment interactions and density dependence, is crucial for predicting plant fitness in changing environments.
• Understanding local adaptation is key to predicting how plant populations, like invasive cheatgrass, will respond to climate change.