Wind pollination over mesoscale distances: an investigation with Scots pine.

There is a gap between the order of magnitude of maximum documented distances of airborne tree pollen transport (up to 10(2)-10(3) km) and effective wind pollination (up to 10(1) km), which may partly derive from greater difficulties in detecting the latter. This study aims to assess wind pollination over scales closer to the maximum observed physical pollen transport distances. The origin of effective pollen immigrants into a strongly isolated Iberian Pinus sylvestris remnant was investigated using paternally inherited microsatellite markers and maximum-likelihood estimation combined with Monte Carlo assessment of parameter uncertainty. The results revealed significant effective pollen flow (up to 4.4%) from a large population located 100 km away, suggesting that the well-known mesoscale airborne transport of viable pine pollen can result in successful pollination over larger scales than previously reported for wind-pollinated tree species. This study supports the view that the gap between documented potential and effective wind pollen dispersal scales might not accurately reflect biological reality. Expanding the expected range of effective wind pollination has an impact on the assessment of a wide range of ecological and evolutionary processes, including reproductive assurance on fragmentation or colonization, metapopulation connectivity and interactions with local adaptation in heterogeneous habitats.