Pollination and Dispersion of Five Species of Lousewort (Pedicularis) near Atkasook, Alaska, U.S.A.

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Abstract
Five spp. of Pedicularis [P. kanei, P. langsdorffii, P. sudetica, P. capitata and P. lapponica] are common near Atkasook, Alaska, and all rely on bumble-bees for pollination. But bumblebees were not abundant in 1975 and 1976, and although most flowers were pollinated (60-95% depending on year and species), only 20-50% of the ovules in pollinated flowers developed. All species shared characteristics that favored outcrossing; all were protogynous, all required an insect vector for pollination and all, except a late-flowering species, produced more seeds when outcrossed that when inbred. Despite a short growing season, 1 species bloomed earlier than the rest and 1 bloomed later than the rest. The early species (P. kanei) had the largest shoots and produced many seeds even though nectar production and pollination success (seeds per ovule) were low. The late species (P. lapponica) had the smallest shoots and produced few seeds even though pollination success was high. Of the species blooming in mid-season, 1 (P. capitata) had few flowers, and thus few seeds per shoot, even though nectar production and pollination success were high; 1 (P. langsdorffii) had large numbers of ovules, high pollination success and the largest number of seeds per shoot; and 1 (P. sudetica) had intermediate number of ovules but low pollination success and low numbers of seeds per shoot when growing in isolated patches. Species that had greater leaf weight per shoot (more photosynthetic material) produced more or seeds so that their total weight seed produced per shoot was larger. Analysis of dispersion patterns indicated that each species reached peak abundance in different habitats and that local spatial overlap (1-m2 quadrats) was slight. These patterns could be interpreted as responses to competitive interactions, but sexual reproduction was less successful in relatively pure stands of a single species than in mixed stands of several species. Apparently, plants in mixed stands benefited from attraction of bees because of the greater density of flowers. Once attracted, individual bees tended to concentrate their foraging on a single species of plant.