Species‐specific use of allochthonous resources by ground beetles (Carabidae) at a river–land interface

Abstract

AbstractA variety of organisms mediate river–terrestrial linkages through spatial subsidies. However, most empirical studies have classified organisms rather broadly (e.g., by functional group or taxonomic family) and have dismissed species‐level linkages at the interface of ecosystems. Here, we show how allochthonous resource use varies among taxonomically similar species of ground beetles (family Carabidae) across seasons (June–September). We investigated seasonal shifts in the distribution of five beetle species and their dietary responses to spatial subsidies (emerging aquatic insects) in a Japanese braided river. Despite their taxonomic closeness, the ground beetles showed species‐specific responses to spatial subsidies, and beetle distribution patterns tended to coincide with their diets. Overall, 1–56% of ground beetle diets were derived from aquatic prey. One genus (Bembidion spp.) mainly consumed aquatic prey, while three species fed primarily on terrestrial prey across all seasons. However, one species (Lithochlaenius noguchii) showed shifts in its diet from aquatic to terrestrial prey according to subsidy availability. The observed variation in allochthonous resource use was likely related to species‐specific foraging modes, physiological tolerance to dry conditions, and interspecific competition. Our findings suggest that considering species‐specific interactions is necessary to fully understand cross‐system interactions and recipient food‐web dynamics.