Fruit and seed set in Mayapple (Podophyllum peltatum): influence of intraspecific factors and local enhancement near Pedicularis canadensis

Abstract

The breeding system and determinants of fruit and seed production in a population of 114 patches of Mayapple (Podophyllum peltatum L.) were examined. Experimental crosses indicated that Mayapple patches are self-incompatible (clones) and that fruit and seed set were pollinator limited. Mayapple flowers are nectarless yet depend primarily on infrequent visits by nectar-searching bumblebees for pollination. The proportion of flowers setting fruit and ovules setting seed in Mayapple clones was inversely associated with the distance to neighboring clones and the distance to Pedicularis canadensis L. plants. Clones within 45 m of P. canadensis plants (which are heavily visited by bumblebees) showed significant increases in fruit and seed production compared with a similar group of more distant clones. This effect is interpreted as evidence for a facilitative interaction between Mayapple and P. canadensis.