Effect of an Invasive Plant Species on the Reproductive Success of a Native Congener

Abstract

Invasive plants may affect the reproductive success of native species in shared habitats via competition for abiotic resources and by altering pollinator behavior. This 2-year study investigates the effect of the presence and density of the invasive plant species Lespedeza cuneata on the pollination and reproductive output of its native congener L. virginica using three groups of metrics: pollinator visitation and assemblage, pollen deposition and pollen tube formation, and pollen limitation of fruit set. No effect was found on pollen deposition, pollen tube formation, fruit set, or pollen limitation as a function of L. cuneata density. Pollinator assemblages had considerable overlap, but the relative visitation of some taxa, most notably Apis mellifera, varied between each species. Notably, A. mellifera was not observed visiting L. virginica in plots where L. cuneata had been removed. These results suggest that while L. cuneata may cause changes in pollinator composition, it neither facilitates nor inhibits the reproduction of L. virginica via pollinator interactions.