Pollen limitation has been demonstrated in many plants. Increasingly isolated plants have a greater risk of pollen limitation as a result of changes in pollinator behavior. Moreover, pollen limitation due to isolation can result in reduced seedset and thus decrease the performance and reproductive output of plants. We studied natural populations of wild cabbage (Brassica oleracea), a self-incompatible perennial, on the Dorset coast, UK. Isolation was defined at the individual scale as the distance to the nearest conspecific neighbor. In a second step, we then introduced artificial isolation by arranging single flowering plants along a transect up to 1,000m from the nearest population.

Results/Conclusions

We found that isolation did reduce the amount of pollen cover on stigmas. However, this did not translate to reduced seedset due to high pollinator activity overcoming the natural scales of spatial isolation. In the artificially isolated plants we saw stronger effects of isolation on pollen limitation that significantly translate into seed set.
We argue that our results are of importance for understanding the complex spatio-temporal dynamics of plant populations. In particular, our results suggest that successful reproduction, i.e. seed set in sufficiently high numbers, is limited for the spatially isolated plants acting as pioneers in population foundation. Therefore, foundation of new populations is not only limited by habitat suitability and dispersal of viable seeds into the patch but also by successful reproduction later on, possibly limited by sufficient pollination.