Reproduction of invasive Amur honeysuckle (Lonicera maackii) and the arithmetic of an extermination strategy

Abstract

Ecological restorations often require removal of invasive species. The abundance of invasives has tended to catalyze research emphasizing removal, not broader understandings, of species mechanisms for persistence in the landscape (e.g. reproductive output and seed dispersal). Asiatic shrub honeysuckles (Lonicera spp.) are pernicious invaders throughout eastern North America. Heavy tree canopy cover apparently reduces growth and reproductive output in Lonicera maackii, which is widespread through the lower Midwestern United States. To help focus control efforts more effectively, we quantified the effect of tree canopy cover on vegetative growth, flowering, and fruit production under three canopy densities. Mean vegetative growth of flowering shoots was not affected by canopy cover. All aspects of sexual reproduction (flower production, fruit set, fruit number, fruit mass, seed number, and seed size) were strongly reduced by moderate shade. Although all individuals modify community and ecosystem properties, a limited number of high light individuals might also provide the greatest proportion of the seeds. Through model simulation of honeysuckle population structure in relation to canopy cover, we argue that it can sometimes be more efficient to initially target reproductive individuals in the high light edge and interior gap environments than to immediately focus on all individuals in the forest interior.