Temperature-Dependent Shifts in Multiple Indirect Defensive Interactions on Black Cherry

Many plants engage in indirect defense via tri-trophic interactions whereby plants provide resources such as food or shelter to mutualists in exchange for protection against herbivores and pathogens, increasing plant fitness. As temperature regimes shift under climate change, understanding the influence of temperature on tri-trophic defensive interactions is increasingly important. However, where plant species host multiple tri-trophic defensive interactions, we still lack an understanding of if each interaction, even within the same system, responds in the same way to temperature. In this study, we monitored black cherry (Prunus serotina) seedlings for 10 weeks under ambient and increased temperatures to explore the effects of temperature on two different tri-trophic defensive interactions between black cherry and: (1) mutualistic leaf domatia-dwelling mites and leaf fungi; and (2) arthropod predators and herbivores. We found that the positive association between mite abundance and domatia size increased by 8.7% on warmed plants, while warming weakened the positive relationship between mite abundance and the abundance of foliar fungi by 14%, though warmer conditions alone did not affect the abundances of any of these groups. Further, warming increased the abundance of arthropod predators by 116% and decreased the amount of herbivory plants experienced by 42%, but did not modify the impact predators had on herbivory. Ultimately, the differences among interacting species with warming did not translate to differences in plant growth, indicating black cherry can be robust to at least some of the variation in species interactions caused by changing temperatures in the short term. These findings illustrate that warming can modify the abundance of, and relationships between, some but not all tri-trophic defensive interactions in a given system, further confirming that temperature does not impact plant interactions uniformly.