Data from: Long distance dispersal and genetic structure of natural populations: an assessment of the inverse isolation hypothesis in peat mosses

It is well accepted that the shape of the dispersal kernel, especially its
tail, has a substantial effect on the genetic structure of species. Theory
predicts that dispersal by fat-tailed kernels reshuffles genetic material
and thus preserves genetic diversity during colonization. Moreover, if
efficient long distance dispersal is coupled with random colonization, an
inverse isolation effect is predicted to develop in which increasing
genetic diversity per colonizer is expected with increasing distance from
a genetically variable source. By contrast, increasing isolation leads to
decreasing genetic diversity when dispersal is via thin-tailed kernels.
Here we use a well-established model group for dispersal biology (peat
mosses: genus Sphagnum) with a fat-tailed dispersal kernel, and the
natural laboratory of the Stockholm archipelago to study the validity of
the inverse isolation hypothesis in spore-dispersed plants in island
colonization. Population genetic structure of three species (S. fallax, S.
fimbriatum and S. palustre) with contrasting life histories and ploidy
levels were investigated on a set of islands using microsatellites. Our
data show (φ’st, AMOVA, IBD) that dispersal of the two most abundant
species can be well approximated by a random colonization model. We find
that genetic diversity per colonizer on islands increases with distance
from the mainland for S. fallax and S. fimbriatum. By contrast, S.
palustre deviates from this pattern, owing to its restricted distribution
in the region affecting its source pool strength. Therefore, the inverse
isolation effect appears to hold in natural populations of peat mosses
and, likely, in other organisms with small diaspores.