Data from: Asymmetric contributions of seed and pollen to gene dispersal in the marsh orchid Dactylorhiza umbrosa in Asia Minor

Orchids differ from other plants in their extremely small and partly
air-filled seeds that can be transported long distances by wind. Seed
dispersal in orchids is expected to contribute strongly to overall gene
flow, and orchids generally express low levels of genetic differentiation
between populations and low pollen to seed flow ratios. However, studies
in orchids distributed in northern Europe have often found a poor
geographic structuring of genetic variation. Here, we studied geographic
differentiation in the marsh orchid Dactylorhiza umbrosa, which is widely
distributed in upland regions from Asia Minor to Central Asia. These areas
were less affected by Pleistocene ice ages than northern Europe and the
orchid should have been able to survive the last ice age in local refugia.
In the plastid genome, which is dispersed by seeds, populations at close
distance were clearly divergent, but the differentiation still increased
with geographic distance, and a significant phylogeographic structure had
developed. In the nuclear genome, which is dispersed by both seeds and
pollen, populations showed an even stronger correlation between genetic
and geographic distance, but average levels of differentiation were lower
than in the plastid genome, and no phylogeographic structure was evident.
Combining plastid and nuclear data, we found that the ratio of pollen to
seed dispersal (mp/ms) decreases with physical distance. Comparison with
orchids that grow in parts of Europe that were glaciated during the last
ice suggests that a balanced structure of genetic diversity develops only
slowly in many terrestrial orchids, despite of efficient seed dispersal.