The influence of riparian invasion by the terrestrial shrub Lonicera maackii on aquatic macroinvertebrates in temperate forest headwater streams

Headwater streams in the midwestern United States are an important ecosystem because they are home to key macroinvertebrate species and serve as the starting point for river systems. According to the river continuum concept, any terrestrial inputs to headwater streams can influence biotic communities and abiotic conditions downstream. Amur honeysuckle (Lonicera maackii) is an invasive shrub species prominent in the midwestern U.S. whose allelopathic properties have proven detrimental to local biodiversity. We hypothesized that increasing L. maackii density along headwater streams would alter the diversity of aquatic macroinvertebrate communities. Five sites located in Montgomery and Miami Counties, Ohio were chosen to represent varying L. maackii density along the banks of headwater streams: one heavily invaded site, two moderately invaded sites, and two reference sites (little to no invasion). This study focused on the EPT taxa (Ephemeroptera, Plectoptera, and Trichoptera), which represent orders of insects whose larvae are known to be sensitive to poor stream water quality. The presence of L. maackii had a significant negative impact on the percentage of EPT individuals. There was no significant effect of L. maackii invasion on the number of families within EPT taxa (EPT Index). We noticed the greatest separation of these metrics as well as macroinvertebrate relative abundance between the heavily invaded site and one reference site. Seasonal effects do not seem to be a significant driver of alterations in EPT assemblages. This study hopes to show that the intensity of L. maackii has effects on macroinvertebrate health, carrying management implications. The results of this study suggest that land managers effectively manage L. maackii invasion so as not to significantly disrupt macroinvertebrate diversity and abundance