Analysis of pollination neighbourhood size using spatial analysis of pollen and seed production in broadleaf cattail (Typha latifolia)

The size of pollination neighbourhoods has important consequences for mating patterns, seed production, gene flow, and patterns of genetic variation across populations. We examined the size of the pollination neighbourhood in a stand of a wind-pollinated clonal plant (Typha latifolia L.; broadleaf cattail) by evaluating spatial patterns of pollen production and seed set by individual shoots. We then simulated spatial patterns of pollen availability to investigate the shape of the pollen dispersal curve. We detected significant positive spatial autocorrelations in seed set over distances up to 5 m. This spatial variation in patterns of seed set appeared to be driven by the local availability of pollen: we found significant cross-correlations between pollen production and seed set over distances of approximately 2m. The simulations supported this inference; simulated pollen dispersal curves fit observed patterns of seed set when similar to 99% of pollen was assumed to disperse over distances less than 2 m. Together, these results indicate that the majority of pollination events occur within very close proximity of pollen sources in T. latifolia. Although within-shoot selfing has long been assumed to be a major pollination mode in T. latifolia, our data indicate that pollination events in the stand were more likely to have involved between-shoot pollination.