Diverse habitats promote coexistence of sympatric predaceous diving beetles in paddy environments

Abstract

Understanding species coexistence is fundamental to community ecology and biodiversity conservation. Diving beetles serve as biodiversity indicators in wetlands, rendering an understanding of their coexistence mechanisms essential for wetland conservation efforts. Previous research in this regard have focused solely on either larvae or adults, neglecting potential spatiotemporal partitioning across life stages. We hypothesized that predatory and less mobile larvae are more likely to compete for resources than scavenging and flight-capable adults, resulting in spatiotemporal niche partitioning among larvae. To address gaps in understanding their spatiotemporal niche partitioning and habitat use, we investigated four dytiscid species—Rhantus suturalis, Hydaticus bowringii, Hydaticus grammicus and Cybister brevis—that are prevalent in Japan and often coexist in paddy environments. This study aimed to clarify their coexistence mechanisms and habitat use to develop the conservation strategies of their populations in paddy environments. Two-year field surveys were undertaken in two paddy fields, an agricultural ditch and a pond in Ibaraki Prefecture, Japan. Adults exhibited similar habitat uses, favoring paddy fields from May to July but seeking refuge in a ditch or pond following paddy field drainage. Conversely, we found spatiotemporal difference of emergence in larval abundance across the four species, which may promote their coexistence in paddy environments. We also observed interspecific differences in the feeding preferences of adult and larval diving beetles, which may help avoid competition. Our results underscore the importance of including diverse habitats in paddy environments to preserve diving beetle species diversity.