Forest fragmentation and reproduction in mayapple (Podophyllum peltatum)

Although habitat fragmentation is known to affect pollinator populations, the impact of fragmentation on potentially pollinator limited plant reproduction is not well established.  We tested the hypothesis that forest fragmentation caused by farming affects the reproductive success of mayapple (Podophyllum peltatum) in Ohio.  Because deforestation increases from east to west in northern Ohio, we predicted that the degree of pollen limitation among mayapple populations would be higher in northwestern Ohio woodlots compared to larger forest tracts in northeastern Ohio.  To test this, seed and fruit set were compared across three northern Ohio counties: Henry, Lorain, and Lake.  Pollen loads on naturally pollinated pistils were examined in Henry and Lake Counties.  In all counties, hand-pollinated flowers had higher fruit and seed set than the control group, indicating pollen limitation of fruit production.  However, the area with the most intensive agriculture and least forest cover (Henry Co.) had the highest fruit and seed set, while the area with the least agriculture and most forest cover (Lake Co.) had the lowest fruit and seed set for both hand-pollinated and control flowers.  Natural pollen loads also were greater on pistils from Henry County than the pistils from Lake County.  Therefore, the expected impact of farming and fragmentation on the reproduction of mayapple could not be confirmed.  While pollination may play a role in limiting mayapple reproduction, other factors are important, too.