Data and code for "Disentangling mechanisms of context-dependent species interactions reveals contrasting effects of rainfall on individual- and community-level strengths of plant competition"
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Paper associated with this archive Citation: Hayashi, K. T., and N. J. B. Kraft. 2026. Disentangling mechanisms of context-dependent species interactions reveals contrasting effects of rainfall on individual- and community-level strengths of plant competition. The American Naturalist. Abstract: Ecological theory predicts that the strength of competitive interactions depends on environmental context, with important consequences for the fitness, coexistence, and distributions of species. However, it often remains unclear how the strength of competition between individuals interacts with species-specific demography to determine the community-level impacts of competition across disparate environments. Here, we disentangle how individual- and community-level mechanisms of plant competition vary with rainfall, an important abiotic factor for terrestrial plants. We experimentally parameterized a model of competition between an annual grass (Festuca microstachys) and forb (Plantago erecta) under water supply treatments emulating variation in rainfall across their geographic ranges. We found that per capita competition was strongest when water supply was limited. In contrast, the total effect of competition, measured as the reduction in low-density population growth rate due to the presence of resident competitors, was greater at higher water supply. This apparent decoupling of per capita competition from total competition reflects asymmetries in fecundity and resulting fitness differences between species. Our work emphasizes the importance of, and presents approaches for, distinguishing between how species interact at the individual level and impact one another at the community level in the study of competition and coexistence in variable environments. Originators Kenji T. Hayashi (1, 2)Nathan J. B. Kraft (2) Department of BioSciences, Rice University Department of Ecology and Evolutionary Biology, University of California, Los Angeles Contact information Kenji T. Hayashikenji.hayashi@rice.edu BioSciences at Rice, MS-140P.O. Box 1892Houston, Texas 77251-1892USA Dates of data collection From: 2022-11-07To: 2023-05-16 Geographic location(s) of data collection University of California, Los Angeles, Plant Growth Center Funding sources NSF DEB 1644641NSF DEB 2022810UCLA EEB Departmental Research Grant
