Interspecific competition amongst three species of large-bodied diving beetles: is the species with expanded distribution an active swimmer and a better forager?

Abstract

The poleward range expansion of species native to lower latitudes brings them into competition with closely related species with overlapping habitat niches that are native to higher latitudes. If species of southern origin dominate in such interspecific competitions, this may cause a decline in closely related native species. Since 2010, there has been an increase in the distribution and rediscovery records of a diving beetle species, Cybister tripunctatus lateralis (Coleoptera: Dytiscidae), primarily in western Japan. This trend suggests that global warming may have a positive influence on the growth and survival of C. tripunctatus lateralis. Here, we compare the behavioural patterns and foraging abilities of three species of diving beetles in genus Cybister: C. tripunctatus lateralis (the species with an expanding distribution), C. brevis (a native species), and C. chinensis (a native species). We found that C. tripunctatus lateralis individuals swim more frequently, find food more easily, and consume more food than individuals of either C. chinensis or C. brevis. Our results suggest that the continued population increase and range expansion of C. tripunctatus lateralis may lead to resource competition with other closely related species.

Dine‐in or take‐away? Scavenging strategies in predaceous diving beetles at different water depths

“…When observing Dytiscus latissimus L. adults at a simulated winter temperature, males were more active than females, and this could be related to the need of males to search for mating opportunities (Vahrushev, 2011). Similarly, a behavioral study on adults of three Cybister species found that Cybister chinensis Motschulsky males and Cybister brevis Aubé males swam more actively than conspecific females in experiments using two or six beetles per tank with a 1:1 sex ratio, whereas such sex-dependent behavior was not found in Cybister tripunctatus lateralis (Fabricius) (Ohba et al, 2022). In the present study, we did not detect significant effects of sex on relevant behavioral responses, which might result from the experimental design that could have excluded the potential influences from any conspecific individual by rearing each D. sinensis adult individually for more than 1 month prior to the experiment and using clean tanks and water for each replicate.…”