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Among the more intriguing topics in general ecology courses are the symbiotic relationships (the ‘-isms’ as I sometimes present them – mutualism, commensalism, and parasitism). Of these, mutualism is typically the most appealing to students. The scenario that different species can not only co-exist, but can also provide essential resources/services for one another, resonates well with all but the least interested in the course. Ultimately, however, there is also the palpable degree of dismay when they discover that these relationships arise from mutual exploitation, rather than from some benign force of nature. A flip-side of this, in many ways a type of dark side of nature, is something most ecology students have experienced directly – the degrading effects of invasive plant species on plant communities. Whether it is a verdant blanket of kudzu (Pueraria lobata) on Carolina pines, Japanese knotweed (Microstegium vimineum) extending beyond paths of the Appalachian Trail, or garlic mustard (Alliaria petiolata) creating a monospecific carpet on the forest floor of a temperate hardwood forest, most students have witnessed this phenomenon, with the more curious asking: why? Why is it that invasive species attain, and then maintain, the edge over their native counterparts? Building on earlier work published out of the same laboratory (Cantor et al., 2011; Brouwer et al., 2015), Hale et al., in this issue of New Phytologist (pp. 542–549) address this very important question, and do so in a creative way, ultimately elucidating a novel explanation that answers this question – at least in part – for eastern hardwood forests, and they do so by invoking one of the more well-known mutualistic relationships: mycorrhizas.


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