The role of life history traits and habitat characteristics in the colonisation of a secondary floodplain by neobiota and indigenous macroinvertebrate species

Modification of streams and rivers has mediated range expansions of several species into areas beyond their natural distribution. In this study, a newly created secondary floodplain channel (SFC), with three connections to the Danube, was used as a model system to compare colonisation by indigenous versus non-indigenous species of macroinvertebrates. Three years after the opening of the channel, it was colonised by 210 taxa. Indigenous species were more abundant than non-indigenous ones, both in the channel as well as in the Danube, and colonisation was mostly determined by habitat characteristics. In non-indigenous species, proximity to the source habitat was the main explanatory variable. Non-indigenous colonisers mostly had indifferent functional traits, in contrast to indigenous macroinvertebrates. These differences were particularly pronounced in amphipods where an equal number of five species per group occurred. The results of this study suggest that the factors determining colonisation patterns of indigenous versus non-indigenous species with similar dispersal abilities can strongly differ. Consequently, the creation of specific habitat structures (gravel-dominated, high current flow, bank vegetation) in restoration of floodplain channels can increase competitiveness of native species valued in conservation, particularly if sufficiently long channels with limited edge effects to the source habitat are built.