Spatial patterns of mating relations in wild cherry (Prunus avium L.)

The spatial distribution of wild cherry is characterized by a mixture of scattered and clumped occurrences. In addition, the mating relations of the species are determined by its capacity for clonal reproduction in combination with its self-incompatibility system and by insect pollination. Common paternity analyses basically take the spatial distances between mates into account, but fail to incorporate structural factors in addition to distance such as the patchiness of individuals. We determined mating relations via mating preferences (proportion of matings realized within a group divided by the proportion of potential matings within that group) in various sizes and forms of clusters. The results did not support the common view that mating frequencies more or less steadily decline with increasing spatial distance between mating partners. In fact, mating took place preferentially among members of intermediate sized clusters. However, preference patterns varied distinctly among individual seed trees depending on the shape of neighboring tree clusters and (possibly) attractiveness to pollinators. Distinct preferences for stand-external pollen parents were observed for seed trees located at the border of the higher density area of the stand with stand-external matings generally exceeding stand-internal matings.