Selective integration advantages when transience is costly: immigration behaviour in an agrobiont spider

Dispersal, and especially movement between the natal and the new environment, is a costly process. Costs are incurred not only during the preparation or transfer phase but also on arrival in a new environment. Such costs comprise, for instance, time costs because of the need to search for a suitable microhabitat or integration costs when immigration occurs in already densely populated habitat. The failure to settle or to integrate may consequently inflate the costs already incurred during emigration and transfer. Therefore, we expect emigrating individuals to have evolved enhanced integration capacities. In our laboratory experiments, dispersive phenotypes of the agrobiont spider Erigone atra were characterized by (1) faster settlement in empty habitat and (2) increased willingness to compete for ownership of already occupied sites. These correlated behaviours point to dispersive phenotypes (1) being likely to experience a selective advantage at settlement and (2) not being a random subsample from the population. These correlated behaviours are predicted to have a strong impact on spatial population dynamics and gene flow.