Does allochthonous leaf litter structure terrestrial cave invertebrate assemblages?

Authors: Campbell, Joshua; TSALICKIS, ALEXANDRA - Auburn University; CUMINALE, ANTHONY - Auburn University; ABBATE, ANTHONY - Auburn University

Submitted to: Journal of Natural History
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2021
Publication Date: 6/16/2021
Citation: Campbell, J.W., Tsalickis, A., Cuminale, A., Abbate, A. 2021. Does allochthonous leaf litter structure terrestrial cave invertebrate assemblages? Journal of Natural History. 55(15-16):1021-1032. https://doi.org/10.1080/00222933.2021.1930226.
DOI: https://doi.org/10.1080/00222933.2021.1930226

Interpretive Summary: Food sources for cave invertebrates are primarily derived from outside the cave and must be transported into caves. Thus, caves are generally described as food limited. However, the quality of food sources has rarely been explored for cave ecosystems. We placed six species of tree leaves into three caves and recorded arthropods that inhabited/utilized the leaves at 30, 60, and 100 day intervals. Additionally, we placed leaf sets near the entrance and within the dark zone of each cave. Percent carbon and nitrogen were determined for each leaf type at each time interval. Although, different leaves contained varying amounts of carbon or nitrogen, invertebrate abundance and richness was similar among the leaf types. Thus, food quality may not be the main driver of terrestrial invertebrate abundance or richness within cave ecosystems.

Technical Abstract: Allochthonous materials are the main sources of nutrients for most cave invertebrate communities. However, scant research exists about the differences in quality of various cave nutrient sources. We investigated whether different types of leaf litter would attract different terrestrial invertebrates within cave ecosystems. We placed six leaf types (Cornus florida- dogwood, Acer saccharum- maple, Pinus taeda- pine, Quercus falcata- southern red oak, Liquidambar styraciflua- sweetgum, and Quercus bicolor- swamp white oak) in three caves in north Alabama. Leaf sets were placed within the twilight and dark zones within each cave and gathered at 30, 60, and 100-day intervals. Invertebrates were removed from leaves and counted. Leaves were dried, weighed, and C/N analyses of leaves were determined. Several leaf types were shown to have significantly different amounts of C and N. However, the most commonly collected invertebrates (e.g., Collembola and Acari) were not affected by the leaf type despite some leaves (e.g., pine) being a lower quality food source. Additionally, no differences in overall invertebrate abundance or taxa richness were found among the leaf types or between the twilight and deep zones. Our data suggests that terrestrial invertebrate abundance is not solely driven by food quality and could be driven by multiple factors.