The evolution of socially modulated dispersal

Dispersal plays a key role in ecology and evolutionary biology, including as a mechanism that reduces local competition. However, dispersers often suffer a fitness disadvantage relative to nondispersers, which may lead individuals to prefer that others disperse rather than dispersing themselves. Hence, if individuals can force their neighbours to disperse, they may be favoured to do so rather than voluntarily dispersing for the good of others. Besides forcing dispersal, individuals might also improve their neighbours’ ability to disperse. Here, we investigate the evolutionary drivers and consequences of socially modulated dispersal. We find that: (1) there are three possible stable evolutionary outcomes, involving only voluntary dispersal, only socially modulated dispersal, or coexistence of the two; (2) although social modulation that does not improve dispersal success can only be favoured if it is less costly than dispersal itself, social modulation that facilitates dispersal can be favoured even if it is highly expensive for the facilitator; (3) facilitated dispersal may, counterintuitively, lead to a reduced overall level of dispersal; and (4) social modulation can be either welcome or unwelcome from the perspective of the disperser. These predictions emphasise that the evolution of dispersal depends on individuals’ abilities to both disperse and modulate.