Warming Effects on Dynamic Interactions of Three Duckweed Species

ABSTRACT Plant interactions critically govern ecosystem structure and stability, with climate warming altering interaction dynamics. This study investigates how these warming‐induced shifts manifest in duckweed communities by examining temperature effects (25°C vs. 35°C) on three species: Spirodela polyrhiza , Lemna minor , and Wolffia arrhiza . Drawing upon the stress gradient hypothesis, we quantified the temporal shifts in intra‐ and interspecific interaction types and strengths using empirical dynamic models to test hypotheses regarding competitive and facilitative responses to elevated temperatures. Our experimental design involved maintaining three duckweed species ( S. polyrhiza , L. minor , and W. arrhiza ) in monocultures and various mixed‐species combinations under two distinct temperature conditions (25°C vs. 35°C) for 40 days. Results showed that facilitation dominated intra‐ and interspecific interactions at both temperature conditions. Warming did, however, reconfigure certain interactions. Specifically, intraspecific interactions in W. arrhiza shifted from competition to facilitation in bi‐culture with S. polyrhiza ; in the tri‐culture, warming shifted S. polyrhiza ↔ W. arrhiza interactions from neutral to facilitative, and W. arrhiza → L. minor interactions from facilitation to competition—a shift that was also observed in the L. minor and W. arrhiza bi‐culture. Facilitation strength in tri‐mixtures increased at 35°C, while interspecific interactions weakened across time. Notably, population stability of S. polyrhiza increased and community stability decreased with stronger interspecific interactions, whereas no such pattern was observed for L. minor or W. arrhiza . The prevalence of facilitation, even under increased warming, indicates a robust underlying tendency for positive interactions within this duckweed community. Our findings highlight that warming restructures duckweed interaction networks via varying dynamic strength between facilitation and competition. 6 Identifying temperature thresholds triggering transitions between facilitative and competitive interaction regimes will be critical for anticipating and managing aquatic ecosystem resilience under projected climate warming scenarios.