Geographic Variation in the Pollination Biology of Passiflora lutea (Passifloraceae)

Like most species of Passiflora, P. lutea is reported to produce one-day flowers with complicated floral movements and requires deposition of non-self pollen for fruit production. Medium sized bees are the most likely pollinators in central Texas. We report on a series of observations and experimental manipulations that compare the reproductive biology of P. lutea in central Arkansas to that reported previously from plants about 800 km distant in central Texas. We observed floral movements and floral visitors, compared fruit production of flowers available to pollinators versus flowers from which pollinators were excluded, and compared fruit production of flowers that were hand-pollinated with self pollen versus flowers that were hand-pollinated with non-self pollen. Floral movements were similar to those of other Passiflora, with flowers opening for one day and styles that usually deflexed to a level below the anthers, presumably facilitating cross-pollination. Some flowers (20%) had styles that did not fully deflex. Movement of floral parts of plants in central Arkansas occurred slightly earlier than in plants in central Texas. Unlike what was observed in a small sample in Texas, we observed a low level of self-compatibility in P. lutea. In contrast to the medium sized bees that were the important pollinators in central Texas, Anthemurgus passiflorae, a small specialized andrenid bee that only forages on P. lutea, was likely the most important pollinator in central Arkansas. Finally, fruit set of plants in central Arkansas was much higher than that reported for plants in central Texas. Thus, this species varies geographically in its reproductive biology