Influence of spatial distribution and size of clones on the realized outcrossing rate of the marsh cinquefoil (Comarum palustre)

Clonal growth is a common feature in flowering plants. As clone size increases, the selfing rate in self-compatible species is likely to increase due to more frequent geitono-pollination events (i.e. pollination among flowers within the same genet). This study investigated the breeding system of the marsh cinquefoil (Comarum palustre) and assessed spatial distribution of clones, clone size and architecture, and their effects on realized outcrossing rates. In addition, pollen dispersal was investigated in two patchy populations. The species breeding system was investigated under controlled conditions through hand pollinations (self- vs. cross-pollination). Using microsatellite markers, an assessment was made of the realized outcrossing rates and the genetic diversity in four natural populations, the clonal structure in two populations within five 15 15 m sampling plots following 05 05 m grids, and the pollen dispersal through paternity assignment tests in those two populations. is a self-compatible species but only presents a low rate of spontaneous self-pollination. The occurrence of inbreeding depression was not detected at the seed set stage ((SS) 004). Clones were spatially clumped (A(C) 060080), with intermediate to no intermingling of the ramets (D-C 040100). Genet size ranged from one to 171 ramets. Patchy populations had low outcrossing rates (t(m) 033046). Large clones showed lower outcrossing rates than small clones. Pollen dispersal mainly occurred within patches as only 17 of the pollination events occurred between patches of 25 m separation. Seedling recruitment events were detected. Genet size together with distances between patches, through increasing geitono-pollination events, appeared to be important factors influencing realized outcrossing rates. The study also revealed seed flow allowing seedling recruitment, which may contribute to increasing the number of new patches, and potentially further enhance gene flow within populations.