When forests change, do the ants that live there change, too?
This is the question that Dr. Sydne Record (Bryn Mawr Biology), Tempest McCabe (BMC ‘16), and others asked in their latest paper “Identifying foundation species in North American forests using long-term data on ant assemblage structure”. This paper formed the foundation of Tess McCabe’s senior thesis in Biology and was the focus of her summer Research Experiences for Undergraduates internship at Harvard Forest funded by the National Science Foundation and Bryn Mawr’s LILAC Program. Tess is now a pursuing her PhD at Boston University.
Ants provide a lot of different services to forests; ants aerate soils, decompose wood, and disperse seeds. However, these services depend on the different community diversity of ants. Dr. Record and colleagues wondered if the death of trees within a forest would change the number of species in that forest or the number of services the ant community provided.
To test this, Record and colleagues collected ants at two sites: one with oaks removed at the Black Rock Forest Future of Oak Forests Experiment and one with hemlocks removed at the Harvard Forest Hemlock Removal Experiment. Then for twelve years, they looked at how ant community diversity changed compared to the same oak and eastern hemlock forests without the tree-removals.
They found that the way the ant community changed depended on the type of forest. When eastern hemlocks were lost, the ant community changed taxonomically and in some of the services the ant community could provide. When oaks were lost, the ant community did not change in terms of species composition or the services that they provide to the forest ecosystem. These results support the hypothesis that eastern hemlock is a foundation species.
Dr. Record’s work implies that different trees have different levels of influence over their surrounding ecosystem. The paper suggests that eastern hemlock defines its ecosystem, and that removing eastern hemlocks has effects that cascade down to the ant-level. Removing an oak has fewer effects. Understanding how the loss of particular tree species will affect an ecosystem is essential for conservation efforts.