Lack of Pollinators Limits Fruit Set in the Exotic Lonicera japonica

The nonindigenous invasive, Lonicera japonica, is a woody vine with a well-documented capacity for vegetative spread. In contrast, few data exist on its potential for establishment by seed. Lonicera japonica is biotically pollinated and xenogamous, requiring pollen from a genetically distinct individual for fruit set. We conducted hand-pollinations to determine if the fruit set of L. japonica in Arkansas was pollinator limited. Naturally pollinated control shoots produced fruit from 17.4% of their flowers, but the hand-pollinated flowers had a fruit set of 78.7%. Shoots with pollinators excluded set fruit on only 2.1% of the flowers. To determine geographic patterns in fruit set we surveyed seven different sites along the western edge of the naturalized range of L. japonica. Average fruit set on primary shoots was 13 ± 4.1% (mean ± se), whereas the secondary shoots averaged 23 ± 6.7%. These results support our conclusion that sexual reproduction in populations of L. japonica along the western edge of its naturalized range is limited by a lack of pollination.