evolution, dispersal, plants
The optimal probability and distance of dispersal largely depend on the risk to end up
in unsuitable habitat. This risk is highest close to the habitat’s edge and consequently,
optimal dispersal probability and distance should decline towards the habitat’s border.
This selection should lead to the emergence of spatial gradients in dispersal strategies.
However, gene flow caused by dispersal itself is counteracting local adaptation. Using
an individual based model we investigate the evolution of local adaptations of dispersal
probability and distance within a single, circular, habitat patch. We compare evolved
dispersal probabilities and distances for six different dispersal kernels (two negative
exponential kernels, two skewed kernels, nearest neighbour dispersal and global
dispersal) in patches of different size. For all kernels a positive correlation between
patch size and dispersal probability emerges. However, a minimum patch size is
necessary to allow for local adaptation of dispersal strategies within patches. Beyond
this minimum patch area the difference in mean dispersal distance between center and
edge increases linearly with patch radius, but the intensity of local adaptation depends
on the dispersal kernel. Except for global and nearest neighbour dispersal, the evolved
spatial pattern are qualitatively similar for both, mean dispersal probability and
distance. We conclude, that inspite of the gene-flow originating from dispersal local
adaptation of dispersal strategies is possible if a habitat is of sufficient size. This
presumably holds for any realistic type of dispersal kernel.