Seeing the forest not just for its trees: Exotic pathogens shift forest communities above ground and below ground

Abstract

Exotic pathogens fundamentally alter ecosystems when they cause large-scale tree declines, but the resulting community-level effects are not well understood. The genus Phytophthora includes many of the most damaging exotic pathogens across the globe. For example, Phytophthora cinnamomi, on the list of 100 of the world's worst invasive species, has caused massive die-off events where it has been introduced (Burgess et al., 2017). It has its greatest impacts in Mediterranean-type climates: causing oak decline in Europe (Vettraino et al., 2002) and California (Garbelotto et al., 2006) and an estimated 40% of the 5710 plant species in Western Australia are susceptible to P. cinnamomi (Shearer et al., 2007). It is clear that exotic pathogens are becoming increasingly problematic across the globe, but less clear is how forest communities will change following large- pathogens. In this issue of New Phytologist, Domínguez-Begines et al. (2020; pp. 588–600) take a community-wide approach to evaluate seedling establishment and survival in an area devastated by P. cinnamomi. This work marks a potential pivot point in the way exotic pathogens are studied, moving from pathogen–single host dynamics to a whole community approach.