Complete outcrossing in a monoecious clonal seagrass

Seagrasses are marine, flowering plants with a hydrophilous pollination strategy. Sinclair et al. study microsatellite DNA markers in order to understand the interactions between clonal structure, mating system and pollen dispersal in two seagrass meadows of Posidonia australis with contrasting local environmental conditions, one being exposed and the other being sheltered. The results show that in a system that appears to rely on chance pollination, all embryos are the result of outcrossed pollination. Pollen is thus being mixed in the water column, with local conditions having little influence on the success and pattern of pollination. Complete outcrossing suggests that post-pollination mechanisms may also be in place to prevent geitonogamous selfing.