TEXT BOX 1 - Traits associated with pathogen susceptibility
Plant traits associated with pathogen resistance, tolerance, and escape will determine susceptibility of invasive plants to novel pathogen accumulation. Resistance is the ability of host plants to inhibit or control pathogen infection, while tolerance is the ability of host plants to adjust their biomass or fitness post pathogen infection to reduce impacts, and escape refers to plant avoidance of contact with pathogens (Veresoglouet al. 2013). Resistance helps host plants prevent or slow down accumulation of pathogens, and tolerance alleviates reduction in fitness with pathogen infection. Many plant traits are associated with resistance and tolerance to pathogens and these can determine long-term population dynamics including population declines.
Here, we review plant traits associated with pathogen susceptibility, which may help predict which invasive plants are more susceptible to novel pathogen attack. We used the TRY database (version 5) to review a broad range of plant traits and organized them into general categories of traits (e.g. leaf traits, root traits, growth traits) (Kattge et al. 2011). We then searched the literature for references showing how these traits can influence pathogen susceptibility (Table 1 and Figure 1). Many of these traits are correlated with one another and can vary along the plant economic spectrum and along with growth-defense trade-offs; therefore, it is not always possible to separate these as the direct drivers of pathogen susceptibility but they can be useful for predictive purposes (Herms & Mattson 1992; Reich 2014; Parker & Gilbert 2018). Below, we first discuss evidence for pathogen resistance, tolerance, and escape with respect to each of the categories of traits. Next, we review examples of pathogen accumulation on invasive plants, and finally propose a framework aimed at explicitly accounting for the relative importance of traits for pathogen susceptibility.