Vertical stratification of overwintering coleopteran communities in dead Acer rubrum branches

Saproxylic insects are a large and diverse functional guild of arthropods that include species dependent on dead wood for overwintering development. While the highest concentration of dead wood within forests is typically on the ground, this debris often originated across the vertical gradient of the forest as dead tree branches where they represented a range of environmental conditions that differed from the forest floor. In January 2022, we harvested all dead wood of 11 large and healthy Acer rubrum (red maple) trees within forest fragments of Western Massachusetts to investigate relationships between their overwintering invertebrate communities and factors that influence physical properties of the branches (height, diameter, length, specific gravity, the presence of bark). Overall, 189 branches 1-16 cm in diameter and up to 9.2 m in length were removed from the trees (4.9-25.5 m above the forest floor) and stored in rearing chambers until the following winter to extract emerged invertebrates. We collected a great diversity of arthropods, including ants, bees, beetles, katydids, mites, parasitic wasps, pseudoscorpions, wood lice, and other taxa. Here, we focus our discussion on modeled responses of the coleopteran community with special attention to factors affecting species composition. We further explore trends associated with less abundant taxa and highlight unexpected inhabitants. Our findings provide insight on the role of dead branches from a common tree species in the eastern United States in supporting a diverse arthropod community.