Exploring fungal invasions: observational and theoretical insights and unanswered questions

Ella Segal , Laurel M Philpott, Sean D O'Gorman, Caitlin N Barnes, Kathleen R Coffman, Tyler W d'Entremont, Joseph D Edwards, Jessica M Hammonds, Martin A. Nuñez, Nahuel Policelli, Ari E Puentes, Hannah B Shulman, J Alexander Siggers, Stephanie N Kivlin

Despite invasive fungi’s dramatic effects on native biodiversity and ecosystem processes, the extent of fungal invasions and the mechanisms behind them are unclear. We address this gap by synthesizing documented global macrofungal invasions to assess which fungal traits and lifestyles contribute to invasions across fungal guilds. Specifically, we analyze global observations of non-native fungi to show the extent of introduced fungal range areas for the first time, finding that EM fungi’s introduced ranges concentrate in Australia and South America, while fungal introduced ranges of saprotrophs and pathogens cluster more heavily in North America. We then consider the unified framework of biological invasions proposed by Blackburn et al. (2011), which describes the stages and barriers non-native organisms must pass through to become invasive, from an explicitly fungal point of view. Finally, we evaluate the extent to which seven established hypotheses explain the mechanisms by which non-native fungi overcome invasional barriers. In doing so, we highlight emerging research priorities, provide insight into common pathways through which fungi become invasive, and spotlight how major fungal guilds may proceed through stages of invasion differently. This work is an important step toward integrating fungi into invasion biology research, and, more broadly, assessing microbial fit into invasion theory that has historically focused on macroorganisms.