Although precipitation patterns have long been known to shape plant distributions1, the effect of changing climate on the interactions of species and therefore community composition is far less understood2,3. Here, we explored how changes in precipitation alter competitive dynamics via direct effects on individual species, as well as by the changing strength of competitive interactions between species, using an annual grassland community in California. We grew plants under ambient and reduced precipitation in the field to parameterize a competition model4 with which we quantified the stabilizing niche and fitness differences that determine species coexistence in each rainfall regime. We show that reduced precipitation had little direct effect on species grown alone, but it qualitatively shifted predicted competitive outcomes for 10 of 15 species pairs. In addition, species pairs that were functionally more similar were less likely to experience altered outcomes, indicating that functionally diverse communities may be most threatened by changing interactions. Our results highlight how important it is to account for changes to species interactions when predicting species and community response to global change.
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Data are available on Zenodo (https://doi.org/10.5281/zenodo.7083314). Data were recorded in Microsoft Excel (v.16.63.1) and analysed in R (v.4.2.0).
Codes are available on Zenodo (https://doi.org/10.5281/zenodo.7083314). Figures and tables were created in R (v.4.2.0).
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We acknowledge the Chumash peoples as the traditional land caretakers of the area where we planted our experiment, and the Gabrielino/Tongva peoples as the traditional land caretakers of Tovaangar (the Los Angeles basin and So. Channel Islands), where UCLA is located; G. Kandlikar, K. Hayashi and M. Vaz for helpful suggestions and stimulating discussions; A. Kleinhesselink and C. Johnson for help with analyses; H. Lindsay, M. Clarke, A. Dhaliwal, G. Kandlikar, K. Hayashi, A. Kleinhesselink, K. McCurdy, A. Hardy, L. Johnsen, M. Browne, J. Cooch, M. Cowen, S. Montague and F. Van Dyke for laboratory and field assistance. The work was funded by the La Kretz Center at Sedgwick Reserve, a UCLA Vavra fellowship and National Science Foundation grants DEB 164461 and 2022810 and 2022213.
The authors declare no competing interests.
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Extended data figures and tables
Extended Data Fig. 1 Effects of water treatment on each competing pairs’ stabilizing niche and fitness differences.
Each species pair shown separately with confidence intervals (+/− 1 SD) for stabilizing niche and fitness differences obtained from bootstrapping. Inside the grey shaded region indicates coexistence, outside indicates competitive exclusion.
Extended Data Fig. 2 Principal component analysis of functional traits from the focal plant community.
Principal component analysis with 23 species and eleven functional traits from previous work at the site10 (Methods). The six species from this study are filled in circles and labeled following Extended Data Table 1. The open circles represent other species in the community. See Extended Data Table 3 for trait descriptions.
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Van Dyke, M.N., Levine, J.M. & Kraft, N.J.B. Small rainfall changes drive substantial changes in plant coexistence. Nature 611, 507–511 (2022). https://doi.org/10.1038/s41586-022-05391-9