Resource limitation and competition shape reproductive allocation and synchrony

The dynamics of reproductive allocation (RA) in herbaceous plant communities, particularly in response to varying environmental conditions such as drought stress and competitive interactions, remain underexplored. This study aims to fill this gap by hypothesising that both belowground resource limitation and the presence of dominant species significantly influence RA strategies within plant communities, leading to different patterns of reproductive synchrony. We also expected different effects of resource limitations on interspecific synchrony in RA compared to intraspecific synchrony. We conducted a mesocosm experiment in an experimental garden over five years, exposing wetland plant communities (one dominant species and three subordinate species) to different drought stress regimes and a dominant removal treatment. The dominant species achieved high RA at wet sites, where conditions were most favourable for generative reproduction. Community‐level synchrony increased under drought, reflecting both resource limitation and the competitive influence of the dominant species, which caused subordinate species to converge in their reproductive strategies. Detrended analyses confirmed that these shifts were not driven solely by temporal trends but represented year‐to‐year co‐fluctuations. Intraspecific synchrony remained high in most species, with some subordinate species further increasing synchrony under drought, whereas the dominant species tended to lose synchrony. Overall, our findings demonstrate that reproductive synchrony at the community level is not only a consequence of intrinsic species strategies but also emerges from hierarchical interactions, with dominant species shaping reproductive dynamics under environmental stress.