Evolution of dispersal capacities during range expansion: size and behaviour matter in an arthropod invading the sub-Antarctic Kerguelen archipelago

The flexibility of movement behaviour was investigated in the nonnative carabid beetle, Merizodus soledadinus, by comparing individuals from well-established populations (residents) to those at the invasion front (dispersers) in the sub-Antarctic Kerguelen archipelago. Morphology-dispersal covariation was tested by examining how morphology translates into dispersal efficiency and endurance by implementing in-field measurements of dispersal path, sinuosity and tortuosity. The activities of the enzymes phosphoglucose isomerase and pyruvate kinase were also measured to compare putative physiological changes associated with dispersal and residence. In general, the results obtained confirmed that insects from more recently invaded habitats were characterized by larger body sizes. Furthermore, adults of M. soledadinus sampled at the invasion front were also characterized by higher locomotor performance, as indicated by longer dispersal paths with less directional changes than their relatives from the founder population. Finally, the activity of the enzyme phosphoglucose isomerase, a powerful estimator of individual dispersal capacity, was higher in insects from invasion fronts. Taken together, our findings consistently indicated that beetles collected from populations at invasion front with the shortest residence times were characterized by enhanced dispersal performance, probably explaining the accelerating range expansion of the species.