Water Stress Strengthens Mutualism Among Ants, Trees, and Scale Insects

摘要: Abiotic environmental variables strongly affect the outcomes of species interactions. For example, mutualistic interactions between are often stronger when resources limited. The effect might be indirect: water stress on plants can lead to carbon stress, which could alter carbon-mediated plant mutualisms. In ant–plant symbioses, host ant colonies that defend them against herbivores. Here we show partners’ investments in a widespread symbiosis increase with across 26 sites along Mesoamerican precipitation gradient. At lower levels, Cordia alliodora trees invest more Azteca ants via phloem-feeding scale insects provide sugars, and better defense carbon-producing leaves. Under have smaller pools. A model trade-offs for partners shows observed strategies arise from costs rare but extreme events herbivory rainy season. Thus, limitation, together risk herbivory, increases strength carbon-based mutualism.