Rachel Standish

Impacts of Phytophthora cinnamomi on quenda and fungal communities.

Phytophthora cinnamomi (Pc) is a soil-borne plant pathogen that has resulted in plant species losses in woody ecosystems around the world. Pc is suggested to alter fauna habitat, which could potentially result in cascading impacts, but these topics are underexplored. A principal aim of my research was to investigate Pc impacts in native jarrah forest, where the quenda (Isoodon fusciventer), a bandicoot species endemic to southwest Western Australia, forages for fungi(e.g., truffles), earthworms, and tubers by digging soil. I predicted that Pc would reduce habitat for quenda and result in a shift in fungal communities across my study sites in the Shire of Mundaring, Western Australia. Pc infestations had almost half as much shrub cover and densities of habitable grasstrees compared with adjacent non-infested areas of jarrah forest. Densities of quenda foraging pits were 35% less in Pc-infested forest, although truffle densities were unchanged. I measured densities by size classes of the canopy-dominant trees, jarrah and marri. These data suggested low recruitment success in Pc-infested forest. In contrast, densities of mature trees were not affected by Pc, possibly because of competitive release (i.e., fewer tree saplings, grasstrees and shrubs). I then used DNA metabarcoding to examine how fungi are affected by Pc. I found shifts in assemblages, with ectomycorrhizal fungi and ericoid mycorrhizal fungi negatively impacted by Pc. Finally, I monitored quenda movements with GPS trackers. While I tracked few quendas overall, fewer quendas were trapped in Pc-infested forest and tracked quendas spent more time in non-infested forest and gardens than in Pc-infested forest. Pc has had cascading effects on the jarrah forest ecosystem by altering quenda habitat and reducing hosts for mycorrhizal fungi. Pc can remain in soil for decades or longer. Planting shrubby, mycorrhizal native plants that are Pc resistant may help to mitigate these impacts.