Compositional attributes of invaded forests drive the diversity of insect functional groups

Authors: TRAYLOR, CLAYTON - University Of Georgia; ULYSHEN, MICHEAL - Us Forest Service (FS); WALLACE, DEREK - Tall Timbers Research Station; LOUDERMILK, ELOISE - Us Forest Service (FS); ROSS, CHRISTOPHER - Tall Timbers Research Station; HAWLEY, CHRISTIE - Us Forest Service (FS); Atchison, Rachel; WILLIAMS, JASON - University Of Florida; MCHUGH, JOSEPH - University Of Georgia

Submitted to: Global Ecology and Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2022
Publication Date: 3/19/2022
Citation: Traylor, C.R., Ulyshen, M.D., Wallace, D., Loudermilk, E.L., Ross, C.W., Hawley, C., Atchison, R.A., Williams, J.L., Mchugh, J.V. 2022. Compositional attributes of invaded forests drive the diversity of insect functional groups. Global Ecology and Conservation. 35(1):e02092. https://doi.org/10.1016/j.gecco.2022.e02092.
DOI: https://doi.org/10.1016/j.gecco.2022.e02092

Interpretive Summary: Forest canopies hold the majority of animal biodiversity globally, but like many other habitats are experiencing declines in biodiversity due to habitat disturbances, including compositional changes due to invasive species introductions. While it is well known that biodiversity promotes ecosystem services such as pollination, decomposition, and water and air filtration, further research is needed to understand how diversity is separately influenced by compositional versus structural components of forest canopies. Advances in terrestrial light detection and ranging (LiDAR) now allows researchers the ability to scan forest plots from the ground, yielding unprecedented information on the spatial arrangement of vegetation below the canopy compared to traditional field measurements. In this study, university (Univ. Georgia, Univ. Florida), federal (Forest Service, ARS), and Tall Timbers land conservancy scientists used terrestrial LiDAR in conjunction with traditional forest measurements to investigate whether invasive shrubs influence insect diversity by creating a dense canopy environment (structural attribute) or through other inherent plant properties (compositional attributes) which may alter the ecosystem. Forest measurements were related to the diversity of four insect groups: wood-boring beetles and ants was reduced with the increasing presence of invasive shrubs, fungus beetle diversity was more adversely affected by dense vegetation, and bees were unaffected by either metric. This suggests that while some insects may be less sensitive to invasive plants than previously thought, invasive shrubs do alter the environment to the detriment of other insect diversity in forest canopies and demonstrates the applicability of using LiDAR in studying insect diversity.

Technical Abstract: Forest canopies are important habitats for animal biodiversity globally. The structural and compositional components of canopies influence biodiversity, and recent advancements in remote sensing have given insight to these relationships. As invasive shrubs alter both the structural metrics (vegetation density and Shannon vertical complexity index) were related to invasive shrub cover. We sampled four insect functional groups using two methods: woodboring beetles, mycophagous beetles, and bees were sampled using flight intercept traps 5 m aboveground, while litter-foraging ants were sifted from leaf-litter. From our generalized linear models, we found that tree composition strongly influenced all groups, though responses varied among functional groups. Woodboring beetles were negatively influenced more strongly be invasive shrub cover than vegetation density and also responded positively to tree and deadwood diversity. By contrast, bees and mycophagous beetles were unaffected by both the structure and composition of invasive shrubs, but were sensitive to tree composition. In the leaf-litter, ants were negatively influenced by invasive shrub cover and were sensitive to tree composition. Thus, the composition of forests is an important driver of insect diversity in our system, but with idiosyncratic responses among functional groups. Our results demonstrate the utility of LiDAR in clarifying the relationship between structure and composition on biodiversity in forest canopies, especially in regards to invasive plants.