Dispersal syndromes can impact ecosystem functioning in spatially structured freshwater populations

Abstract

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 twopatch 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.Little, Fronhofer & Altermatt 3

Plastic cell morphology changes during dispersal

“…We have used an experimental approach linking ecological and cell biology competencies to determine how innate and plastic changes to fine-scale cellular activities can impact the dispersal process. Deciphering the mechanisms underlying a repertoire of intra-specific dispersal strategies is a critical step to understand dispersal evolution (e.g., how species modulate their dispersal response when facing environmental changes, or how variability in dispersal syndromes impacts ecosystem function or metapopulation dynamics) 42,49 .…”

Landscape connectivity alters the evolution of density-dependent dispersal during pushed range expansions

“…Pushed and pulled expansions can differ in (relative) speed, genetic diversity (Dahirel et al, 2020) and, as our results show here, phenotypic composition. Lineages/individuals with different dispersal strategies may also differ in traits influencing population stability (Jacob et al, 2019) or ecosystem functioning (Cote et al, 2017; Little et al, 2019). Understanding what environmental conditions favour or disfavour the evolutionary maintenance of “pushiness” during expansions may help more generally to understand the evolution of many traits during range expansions, and the possible functional effects of expanding species on ecosystems.…”

Dispersal syndromes affect ecosystem functioning in ciliate microcosms

“…Dispersal syndromes can also modulate ecosystem functioning through trophic interactions when resource use differs between residents and dispersers (Cote et al 2017b). Hence, primary evidence emerged, showing that dispersers of Dikerogammarus villosus -a freshwater amphipod decomposer- consume more detritus than residents, increasing the decomposition rate of organic material in colonizing habitats (Little et al 2019). Interestingly, effects differed between the two related study species, suggesting that the effects of dispersal syndromes on ecosystem functioning might be species-dependent.…”

“…We further tested whether intraspecific variability in dispersal syndromes (i.e., differences between genotypes in the measured dispersal-related traits) mediates these ecosystem effects. We expected dispersal syndromes to affect biomass production because of functional differences between dispersers and residents (Little et al 2019), and we expected that these effects might be genotype-dependent if the traits associated with dispersal vary among genotypes.…”