Résumé
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.