Leaf characteristics
Leaf traits vary along the leaf economic spectrum from costly leaves with long lifespan and high leaf mass per area (LMA) to quick-return, short-lived leaves with high photosynthetic rates and nitrogen content (Wright et al. 2004). Species that invest in quick-return leaves are relatively more susceptible to pathogen attack (Welsh et al. 2016). However, quick-return leaves may also have faster leaf expansion rate than well defended slow-return leaves, which has been associated with lower pathogen damage, indicating a possible trade-off (Marquis et al.2001). Plant species that minimize potential points of entry for pathogens such as stomata number, invest in leaf defense traits that protect against pathogens ( e.g., thickened cuticle and higher trichome density) and hold water to a minimum (e.g., hydrophobic leaves with low surface moisture) are less susceptible to pathogen attack (Bradley et al. 2003; Chattopadhyay et al. 2011; Serrano et al.2014). Data on leaf traits and pathogen susceptibility have focused specifically on a few species and it is not clear to what extent they are applicable to a wider variety of species, including natives versus non-natives.
Fungal endophytes have also been shown to provide protection against pathogens (Dini-Andreote 2020). For example, the mutualism between temperate grasses and fungal endophytes such as Epichloƫ spp. can defend against pathogens, however more research on host-endophyte-pathogens interaction is needed in the context of invasions (Clay & Schardl 2002; Schardl et al. 2004). For example, we lack biogeographic home and away comparisons between populations for the presence and functional ecology of endophytes. We also lack an understanding of to what extent endophytes of non-native species contribute to competition with native plants through increased pathogen resistance and tolerance of their hosts.