Do mycorrhizal associations mediate garlic mustard (Alliaria petiolata) growth under climate change?

Alliaria petiolata (garlic mustard) is an invasive species that has become well established in forests across eastern North America. It is known to disrupt mutualistic relationships between native plants and arbuscular mycorrhizal fungi (AMF). Historically classified as a non-mycorrhizal species, A. petiolata was thought to gain a competitive advantage by suppressing these symbioses in native flora (Koch et al. 2011). However, recent findings suggest that A. petiolata may experience indirect or context-dependent benefits in the presence of AMF (Trombley et al. 2025), challenging earlier assumptions about its ecological strategies. This experiment investigates whether A. petiolata benefits from AMF—either directly or through root associations with a nearby AMF host species, Acer saccharum (sugar maple)—and whether these interactions are influenced by climate change. Understanding these relationships is key to predicting how this species will behave and impact ecosystems under changing environmental conditions. First-year A. petiolata rosettes were cultivated either in groups of six or surrounding an A. saccharum sapling. Likewise, A. saccharum saplings were grown either alone or surrounded by six A. petiolata rosettes. Plots were maintained outdoors within a fenced area, and either left open or enclosed within open-top chambers to simulate warming associated with climate change. Measurements were recorded every three days and included plant height, length and width of the largest leaf, total leaf count, and observational notes on damage, herbivory, and fungal infection. At the conclusion of the experiment, plots were stratified based on average sunlight exposure and randomly selected for harvest. In each selected plot, above- and below-ground plant material was collected, cleaned, pressed, dried, and prepared for root staining. Findings from this study will offer insight into the invasive potential of A. petiolata and its ability to exploit mycorrhizal networks under future environmental conditions.