Effect of population spatial structure on pollination and seed set of a clonal distylous plant, Persicaria japonica (Polygonaceae)

In order to assess the mechanisms through which the spatial structure of th e population influences female reproductive success, spatial distribution o f clones, degrees of limitation of legitimate (inter-morph) pollination, ty pe and abundance of pollen loaded on the stigmas, and seed set were measure d for many clones of two natural populations of the distylous clonal plant, Persicaria japonica. Within the populations, according to the spatial rela tion to the nearest opposite morph clone, individual clones were assorted i nto two spatial types, i.e., clones that congregated with clones of the opp osite morph (congregating clones), and clones that occurred singly at a con siderable distance from the nearest opposite-morph clone (single clones). T he pollination success, i.e. the proportion of legitimately pollinated flow ers, and seed set were severely limited in the single clones compared to th e congregating clones. Since artificial legitimate pollination improved the seed set in single clones, at least to some degree pollination failure was responsible for the reduced seed set in the single clones.