Pollination ecology of the high latitude, dioecious cloudberry (Rubus chamaemorus; Rosaceae)

Abstract

In a 3-yr study, we examined the pollinator guild and intersexual floral characteristics of the dioecious, perennial cloudberry (Rubus chamaemorus), which flowers in early spring. The findings contribute to our general understanding of pollination ecology at high latitudes and provide important information for the commercialization of cloudberry. Female flowers were smaller than males but provided more nectar, although this resource was low in both sexes. Insects from 43 families visited cloudberry flowers, yet four families (Apidae, Halictidae, Muscidae, Syrphidae) represented ca. 87% of all visitors observed. Introduction experiments revealed that apids and muscids are significantly poorer pollinators (based on fruit production) than halictids and syrphids, but when fruit mass or seed set was considered, there were no significant differences between families. Pollinator importance, a product of flower visitation frequency and seed set effectiveness, revealed that the dipterans were of paramount importance to the pollination of cloudberry. Furthermore, they are limited to cloudberry because their lapping mouthparts exclude them from accessing the nutritional rewards of competing Ericaceae flowers. While the total number of pollinator families observed suggest a generalist pollination system, if one considers the dominant pollinators (flies) as a functional group, then this insect-flower relationship could be considered a specialized one.