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Growth-defense tradeoffs shape the genetic composition of aspen forests

Citation

Cope, Olivia (2021), Growth-defense tradeoffs shape the genetic composition of aspen forests, Dryad, Dataset, https://doi.org/10.5061/dryad.x95x69phb

Abstract

All organisms experience fundamental conflicts between divergent metabolic processes. In plants, a pivotal conflict occurs between allocation to growth, which accelerates resource acquisition, and to defense, which protects existing tissue against herbivory. Tradeoffs between growth and defense traits are not universally observed, and a fundamental prediction of plant evolutionary ecology is that context-dependence of these tradeoffs contributes to the maintenance of intraspecific variation in defense. This prediction has rarely been tested, however, and the evolutionary consequences of growth-defense tradeoffs in different environments are poorly understood. Here we show that intraspecific trait tradeoffs interact with competitive environment to drive natural selection of tree genotypes corresponding to their growth-defense phenotypes. Our results show for the first time that a functional trait tradeoff, when coupled with environmental variation, causes real-time divergence in the genetic architecture of forest stands. Specifically, competitive selection for faster growth resulted in dominance by fast-growing tree genotypes that were poorly defended against natural enemies. This outcome is a signature example of eco-evolutionary dynamics: competitive interactions affected microevolutionary trajectories on a timescale relevant to subsequent ecological interactions. Eco-evolutionary drivers of tree growth and defense are thus critical to stand-level trait variation, which structures communities and ecosystems over expansive spatiotemporal scales.

Funding

U.S. Department of Agriculture, Award: WIS01842

National Science Foundation, Award: DEB-1456592

National Science Foundation, Award: DGE-1747503