Heterospecific‐neighbor‐mediated changes in density and size increase prey capture by a carnivorous plant

Prey capture by carnivorous plants is influenced by plant traits, environmental factors and interactions with animals. However, little is known about how interactions with heterospecific plant neighbors affect prey capture. Here, we examined how prey capture by the carnivorous plant pink sundew Drosera capillaris was influenced by its dominant flowering neighbor yellow hatpin Syngonanthus flavidulus via two mechanisms: 1) changes in the density and size of sundews and 2) changes in the surrounding prey resource availability resulting from the attraction of insects to the flowerheads of S . flavidulus . In a seasonal pond habitat, we surveyed D. capillaris density, rosette diameter and prey capture, along with insect communities, across habitat patches with varying S. flavidulus densities. We also experimentally removed S . flavidulus flowerheads to test the effect of neighboring flowers on prey availability. We found that D. capillaris density was negatively associated with S . flavidulus density. Moreover, the rosette diameter of D. capillaris decreased with increasing intraspecific density, resulting in high densities of smaller‐sized sundew individuals in the habitat with few S. flavidulus and low densities of larger‐sized sundew individuals in the habitat with abundant S. flavidulus . Such variation in D. capillaris density and size influenced its prey capture, with sundews (low densities but larger‐sized) in the habitat with high S. flavidulus densities capturing more prey items per area. We found no differences in the insect abundance or composition among habitats with varying S. flavidulus densities. Furthermore, experimental removal of S. flavidulus flowerheads did not alter prey availability compared to the unmanipulated habitats, suggesting flowerhead attraction did not alter the local prey resource pool. Our study provides novel insights into the ecological mechanisms underlying prey capture in carnivorous plants, underlining how interactions with heterospecific neighbors can drive density‐ and size‐dependent prey resource acquisition.