Microhabitat use by white-footed mice Peromyscus leucopus in forested and old-field habitats occupied by Morrow's honeysuckle Lonicera morrowii

We quantified microhabitat use by white-footed mice Peromyscus leucopus in forest and old-field habitats occupied by Morrow＇ s honeysuckle Lonicera morrowii, an invasive exotic shrub imported from Japan. Microhabitat characteristics were compared between trails used by mice （ n = 124） and randomly selected trails （ n = 127） in 4 study plots located at Fort Necessity National Battlefield, Farmington, Pennsylvania, USA. We compared 10 mierohabitat variables between used and random trails using non-metric multidimensional scaling （NMDS） and classification and regression tree （CART） analysis. Trails used by mice were statistically different from randomly selected trails in both forested plots （ P 〈 0. 008） and old-field plots （ P 〈 0. 001 ）. In the forested plots, trails of white-footed mice were more often associated with a greater percent cover （% cover） of coarse woody debris （CWD） than were randomly selected trails. In the old-field plots, mouse trails were commonly characterized by having a lower % cover of exotic herbaceous vegetation, a greater % cover of shrubs, and a greater % cover of Morrow＇ s honeysuckle than randomly selected trails. Our study indicates that white-footed mice do not move randomly and prefer areas of high structural complexity, thereby showing significant microhabitat preference. The preference of white-footed mice for areas with a relatively high percent cover of Morrow＇s honeysuckle could 1 ） be a factor in the aggressive nature of the exotic honeysuckle shrub＇s spread throughout the Battlefield or 2） cause the shrub to spread even faster into adjacent areas not yet occupied by Morrow＇ s honeysuckle

Invertebrate Abundance, Biomass, and Richness Associated with an Exotic Invasive Shrub (Lonicera morrowii A. Gray)

Exotic bush honeysuckles (Lonicera spp.) are becoming increasingly common in the eastern and mid-western United States, but little is known about their impacts on invertebrates. We used a modified leaf vacuum to sample invertebrates in the shrub strata and understory of three shrub types (and open plots in the understory): single Morrow’s honeysuckle (L. morrowii A. Gray) shrubs, single native southern arrowwood (Viburnum recognitum Fernald) shrubs, and dense thickets of Morrow’s honeysuckle, in southwestern PA, USA during 2004 and 2005. We also assessed the degree of herbivory on the two species of shrubs. Within the shrub strata, invertebrate biomass was lower in southern arrowwood shrubs, but there was no difference in invertebrate abundance or family richness. Invertebrate abundance and richness were lowest in August, but there was no difference in biomass among the months. Invertebrate abundance, biomass, and family richness were lowest in the understory below dense thickets of Morrow’s honeysuckle. Overall, the percent cover of herbs was the proximate factor responsible for driving patterns of invertebrate abundance, though ultimately these patterns were being driven by shrub type. Abundance and biomass of larval leaf chewers were highest in the native shrub;Morrow’s honeysuckle had a mean of 29.7 cm2 of leaf area consumed per 1 m2 of leaf area, while the native shrub had a mean of 284.3 cm2 of leaf area consumed. Our results suggest that areas dominated by the exotic shrub negatively impact invertebrate biomass, which may in turn affect organisms at higher trophic levels.