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.

Photosynthesis and shoot allocation of amur honeysuckle and two native shrubs in deep shade

“…Based on gas exchange data and leaf characteristics, honeysuckle clearly nds near optimal habitat along forest edges. This supports Schulz and Wright's (2015) suggestion that control of edge shrubs should be a conservation priority.…”

“…Commonly honeysuckle establishes in forest edges and damaged stands where the canopy is relatively open , Henken et al 2013. High light conditions support rapid growth and copious seed production (Luken et al 1997, Schulz andWright 2015), with ready populations of animal vectors to disperse seed (Ingold andCraycraft 1983, Vellend 2002, Gorchov 2006, Castellano andGorchov 2013). Because honeysuckle has a reasonable level of shade tolerance, it can persist in the understory and capitalize on natural canopy openings for further growth and establishment opportunities (Henken et al 2013).…”