Dispersal can strongly influence ecological and evolutionary dynamics. Besides the direct contribution of dispersal to population dynamics, dispersers often differ in their phenotypic attributes from non-dispersers, which leads to dispersal syndromes. The consequences of such dispersal syndromes have been widely explored at the population and community level, however, to date, ecosystem-level effects remain unclear. Here, we examine whether dispersing and resident individuals of two different aquatic keystone invertebrate species have different contributions to detrital processing, a key function in freshwater ecosystems. Using experimental two-patch systems, we found no difference in leaf consumption rates with dispersal status of the common native species Gammarus fossarum. In Dikerogammarus villosus, however, a Ponto-Caspian species now expanding throughout Europe, dispersers consumed leaf litter at roughly three times the rate of non-dispersers. Furthermore, this put the contribution of dispersing D. villosus to leaf litter processing on par with native G. fossarum, after adjusting for differences in organismal size. Given that leaf litter decomposition is a key function in aquatic ecosystems, and the rapid species turnover in freshwater habitats with range expansions of non-native species, this finding suggests that dispersal syndromes may have important consequences for ecosystem functioning.

Suppdata1_G_fossarum_bodyweightsBody weights of Gammarus fossarum individuals used in the experimentSuppdata1_G_fossarum_dispnet_bodyweights.csvSuppdata2_GF_weight_and_survivalLeaf consumption rates by Gammarus fossarum individuals, and their survival, over a roughly two-week experimentSuppdata3_DV_weight_and_survivalLeaf consumption rates by Dikerogammarus villosus individuals, and their survival, over a roughly two-week experimentSuppdata4_D_villosus_bodyweightsBody weights of Dikerogammarus villosus individuals used in the experimentSuppdata4_D_villosus_dispnet_bodyweights.csv