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

Authors: VAHSEN, MEGAN - Utah State University; VAN EE, JUSTIN - Colorado State University; GAMBA, DIANA - Pennsylvania State University; MAXWELL, TOBY - Us Geological Survey (USGS); PIRTEL, NIKKI - Utah State University; ROMERO, SETH - University Of Nevada; BARNETT, DAVID - National Ecological Observatory Network (NEON); BAUGHMAN, OWEN - Collaborator; ENSING, DAVID - Agriculture And Agri-Food Canada; GILL, RICHARD - Brigham Young University; HOLDREGE, MARTIN - Utah State University; HUFBAUER, RUTH - Colorado State University; HUFFT, REBECCA - Denver Botanic Gardens; MOFFAT, CHANDRA - Agriculture And Agri-Food Canada; OTT, JACQUELINE - Rocky Mountain Research Station; PYLE, LYSANDRA - University Of Alberta; SCHROEDER, CORINNE - The Nature Conservancy; SCHUPP, EUGENE - Utah State University; SHRIVER, ROBERT - University Of Nevada; STEMKOVSKI, MICHAEL - Utah State University; SYMSTAD, AMY - Us Geological Survey (USGS); URZA, ALEXANDRA - Us Forest Service (FS); BLUMENTHAL, DANA - Retired ARS Employee; BROWN, CYNTHIA - Colorado State University; GERMINO, MATTHEW - Us Geological Survey (USGS); HOOTEN, MEVIN - University Of Texas At Austin; LASKY, JESSE - Pennsylvania State University; LEGER, ELIZABETH - University Of Nevada; Porensky, Lauren; ADLER, PETER - Utah State University

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: The annual grass cheatgrass is an invasive species affecting rangeland productivity across western North America. While it's range appears to be expanding, risk of invasion is not well understood for this species, and may be linked to genetics. This study used multiple experimental plots across a range of environmental conditions and a dozens of genotypes to characterize how genetics shape the species' tolerance of different climate conditions. Cheatgrass responses to climate were highly related to genetic differences, with high variation across genotypes. This suggests that that limiting the introduction of novel genotypes might be important in limiting the species potential to invade new areas.

Technical Abstract: Characterizing the relationship between climate variables and fitness is essential for predicting how plant populations will respond to future climatic conditions, though such relationships can be challenging to quantify. This may be due to important biotic factors that mediate the relationship between climate and fitness. For example, genetic variation can mediate fitness responses, as genotypes may respond differently to the same abiotic factor, potentially as a function of their source climate (i.e., local adaptation). Additionally, populations can have density-dependent responses to climate. Interactions between local adaptation and density dependence, though understudied, may also shape fitness responses. We conducted a replicated common garden experiment (four sites × two years) with 96 genotypes (n = 22,492 individuals) of the invasive annual grass Bromus tectorum (cheatgrass) to understand how eco-evolutionary context contributes to the climate–fitness relationship. We grew genotypes in varying soil microclimate conditions by manipulating surface albedo, and at two planting densities. We calculated a “climate mismatch” metric for each genotype within each common garden treatment to characterize the role of local adaptation to climate in explaining variation in fitness. Genotype-by-environment interactions improved the predictive accuracy of our hierarchical model, and there was strong evidence of local adaptation to climate across genotypes. Survival responses to soil microclimate were density-dependent, however combined with seed production, there were no density-dependent responses to climate for overall fitness. There was stronger evidence for local adaptation at lower compared to higher planting density. Fitness was maximized when the garden environment was hotter and drier than a genotype’s source climate, but only at high density. Assuming a 2°C increase in soil temperature across all genotype source populations, our model generally predicts increases in fitness, though the magnitude varied substantially. Our findings suggest that eco-evolutionary context can obscure fitness responses to shifting weather conditions and should be accounted for in future predictions.