Combined empirical techniques reveal key role for variation in plasticity in a novel environment

Abstract

As climate change alters environments, species may need to adapt, plastically respond or move into different habitats to persist. Understanding these responses is essential for predicting which species are most under threat of extirpation (loss in a particular location), and which should be prioritized for conservation. However, testing species' responses is often difficult due to the logistical constraints of introducing a population into a new location, and the temporal scale required to test for adaptation. A novel approach examining the impact of variation in plasticity on the adaptive capacity of a population is used by Walter et al. (2023; pp. 374-387) in a new article published in this issue of New Phytologist. Coupling a large-scale beyond-range transplant experiment with a transcriptome analysis, the authors find that existing genetic variation in plasticity within the range can improve fitness and adaptive potential when transplanted into a novel environment. Walter et al. collected cuttings of Senecio chrysanthemifolius from five sites in the core of its elevational range (c. 500-800 m above sea level (asl)), and then transplanted 8149 clones of 314 genotypes across three sites along an elevation gradient, including one site beyond the species' upper range limit (c. 2000 m asl). Mean fitness and variance in absolute fitness declined drastically beyond the limit, but variance in relative fitness among genotypes increased. The existing genetic variation for plasticity within the range improved adaptive potential in the beyond-range environment, despite fitness declines. The authors found that top-performing genotypes beyond the range generally suffered lower fitness within the range, suggesting a tradeoff. These genotypes also differentially expressed more genes than genotypes with low beyond-range fitness, which interestingly translated into lower plasticity for most leaf traits. The impressive sample size of transplants yielded novel insights into the ability of existing variation in plasticity to improve adaptive potential beyond the range, with important implications for range expansions.