Mate-finding dispersal reduces local mate limitation and sex bias in dispersal

1. Sex-biased dispersal (SBD) often skews the local sex ratio in a population. This can result in a shortage of mates for individuals of the less-dispersive sex. Such mate limitation can lead to Allee effects in populations that are small or undergoing range expansion, consequently affecting their survival, growth, stability and invasion speed.

2. Theory predicts that mate shortage can lead to either an increase or a decrease in the dispersal of the less-dispersive sex. However, neither of these predictions have been empirically validated.

3. To investigate how SBD-induced mate limitation affects dispersal of the less-dispersive sex, we used Drosophila melanogaster populations with varying dispersal propensities. To rule out any mate-independent density effects, we examined the behavioral plasticity of dispersal in presence of mates as well as same-sex individuals with differential dispersal capabilities.

4. In the presence of high-dispersive mates, the dispersal of both male a...