Can δD and δ¹⁸O stable isotopes be used to detect long-range dispersal among carabid beetles?

We studied if hydrogen (δD) and oxygen (δ¹⁸O) stable isotope values in three common carabid species in intensively managed agricultural landscapes in southernmost Sweden indicate long-range dispersal. We matched “emerging” (emergence tents) and “colonizing” (pitfall traps) individuals of three carabid species (Trechus quadristriatus, Harpalus rufipes, Pterostichus melanarius) to account for spatial and seasonal variability. There was higher dispersion of δD values among H. rufipes individuals as compared to values of the other two species, which suggests that H. rufipes individuals had the most variable spatial natal origin. The δD values were significantly lower among colonizing compared to emerging individuals in the flight capable and carnivorous species T. quadristriatus. This result suggests long-range migration of T. quadristriatus individuals from remote locations with deuterium depleted (lower δD) meteoric water. Our study provides a first effort towards understanding the δD and δ¹⁸O dynamics in epigean carabids in northern European agroecosystems. Additional research on larger (preferably continental) spatial scales and experimental trials that attempt to disentangle major unaccounted sources of variation and decoupling of δD and δ¹⁸O among carabids and other invertebrate natural enemies is urgently needed to allow a more frequent use of δD and δ¹⁸O dynamics as indicators of long-range dispersal.