BEE: Consequences of phenotypic plasticity for gene-to-ecosystem linkages: Multi-stress experiments across the climatic range of a foundation species

Northern Arizona University, Flagstaff AZ

Investigators

Abstract

Predicting how ecosystems will respond to environmental change is a major challenge for environmental scientists. One strategy is to focus on the traits (characteristics) of organisms that play the most critical roles in their ecosystems. Along rivers, key tree species such as cottonwoods provide shade, habitat, and food for a wide range of other species. Many types of insects feed on the leaves and on the litter that falls in the river. The traits of the leaves impact the survival of these insects, which then impacts birds and fish higher up the food chain. Past research shows that leaf traits like leaf size and chemistry are partly determined by a tree's genes. However, little is known about what will happen to these traits as the environment changes. Using Fremont cottonwood trees from across Arizona, this research will assess how trees have evolved to tolerate environmental stresses in the past, including both changing temperatures and attacks from insects. This information about a tree's history of stress will then be used to predict the role it will play under future environmental stress. The results will aid ongoing river restoration projects across the Southwest by helping identify the types of trees that should be planted to support healthy ecosystems. Genetic variation within foundation species is a major source of diversity in functional traits, which in turn shape community structure and ecosystem processes. However, individual genotypes may express different trait values when exposed to environmental change. This phenotypic plasticity can differ among genotypes as an evolved response to climatic variability or herbivore activity, producing genotype x environment (G x E) interactions. This research will test the hypothesis that understanding the evolution of plasticity in locally adapted genotypes will enhance prediction of the impacts of genetic variation at a broad landscape scale. First, the research will use three existing common gardens to investigate how genotypes of a southwestern tree species express different leaf traits in hot vs. cold conditions. Across all gardens, experimental manipulation of herbivore damage will be used to investigate interactive effects of abiotic and biotic stress on multiple leaf traits. Second, the project will test how variation in traits can be predicted from past variation in the environment at each genotype's home location. Finally, litter transplant experiments and surveys will be used to quantify the impacts of changing leaf traits on whole communities of terrestrial and aquatic insects dependent on these trees. Investigating feedbacks between the evolutionary causes and ecological consequences of phenotypic plasticity across a species' range should greatly improve our ability to predict ecosystem persistence across a rapidly changing landscape. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.