POLLEN LIMITATION AND LOCAL HABITAT-DEPENDENT POLLINATOR INTERACTIONS IN THE INVASIVE SHRUB LONICERA MAACKII

Many nonnative plants require pollinators to produce the seed needed to establish beyond their native range. Local variation in pollination can cause variation in mating patterns, reproductive output, genetic diversity, and selection, which can influence invasion dynamics. We quantified pollinator visitation, pollen deposition, and pollen limitation of reproduction in the invasive shrub Lonicera maackii in adjacent forest edge and forest interior habitats. Flowers in edge habitats received as many or more pollinator visits than those in interior habitats, resulting in twofold greater pollen deposition and nearly twice as many seeds produced per flower. Supplemental pollination increased seed production over open pollination by 37%-145% in both edge and interior habitats. Edge flowers produced more seed than interior flowers. Despite greater pollen deposition in edge habitats, the magnitude of pollen limitation was similar to interior plants. Thus, different mechanisms of pollen limitation characterize these habitats. Pollen receipt and other resources limited reproduction of interior plants, which were located in a shady environment. Pollen quality likely limited reproduction of edge plants, because pollinators visited more flowers per plant and likely delivered more geitonogamous pollen in this habitat than in the interior. Therefore, local variation in abiotic conditions influenced reproduction in this invasive plant, both directly and indirectly via pollinators.