Integration benefits when transfer is costly: Dispersive phenotypes are superior competitors

Background/Question/Methods   Understanding the causes and consequences of dispersal is elementary to understand ecological and evolutionary patterns in modern spatial ecology. Instead of considering dispersal solely as the movement of organisms away from their natal habitat, it has become clear that dispersal should be regarded as a three-stage life history trait including transfer (movement), emigration (preparation of the eventual movement) and immigration (finalisation of the movement phase in novel habitat by settlement). Because individuals may take decisions on the eventual dispersal process before, during and after their movement away from the natal habitat, it is obvious that costs and benefits during each of these stages will eventually shape the dispersal strategy. On average, fitness of dispersive phenotypes should equal that of their philopatric conspecifics. However, the fitness of established dispersers should only be equal to those of the residents when dispersal is completely free of costs. The cost of dispersal hypothesis predicts that, because dispersal is costly, individuals should only leave home in favour of an alternative habitat when potential fitness in the alternative exceeds that in the home by a value greater than the cost of dispersal.

Results/Conclusions   I show by a set of laboratory experiments and individual based modelling that spiders inhabiting arable landscapes are ‘superdispersers', with individuals possessing superior competitive abilities taking the risk of ballooning (i.e., a risky aerial dispersal behavior). By considering traits related to settlement as an integral part of the entire dispersal process, our results subsequently indicate the existence of dispersal syndromes, with individuals showing a large willingness to engage in long distance dispersal being superior competitors once settled. The fact that dispersive individuals are not a random subsample from the populations has pronounced consequences for the genetic structure and dynamics in metapopulation.