Pollinators, seed predators, and grazers influence selection on floral display of Primula farinosa

In plants, a conspicuous floral display may increase attractiveness to pollinators, but also the risk of damage by seed predators and grazers. We examined how interactions with mutualists and antagonists influence reproductive success in Primula farinosa, which is dimorphic for inflorescence height. This perennial herb produces either a regular or a very short scape. We monitored fruit initiation, and damage from grazers and seed predators, in 80 P. farinosa populations on the island of Öland, SE Sweden, over a six-year period. Supplemental hand-pollination demonstrated that fruit production was more strongly pollen limited in the short-scaped than in the long-scaped morph. However, this disadvantage was in several populations balanced by a lower risk of damage from grazers and seed predators. Fruit initiation and seed predation varied among populations, creating a selection mosaic. The effects of grazing on population dynamics and the evolution of scape morph frequency are currently examined in a field experiment.