Giles Hardy

Does predation risk to critical weight range mammals increase in

Phytophthora cinnamomi-infested areas? Phytophthora cinnamomi, a plant pathogen, poses a severe threat to native flora in Australia, resulting in substantial vegetation loss and the degradation of fauna habitats. This habitat loss may benefit introduced predators like red foxes and feral cats, as previous research has shown that they prefer hunting in degraded or cleared habitats. The combined effects of P. cinnamomi-induced habitat loss and increased predator activity could have detrimental consequences for native wildlife, particularly those within the critical weight range (CWR) of 35g to 5.5kg. In Mundaring, Western Australia, P. cinnamomi-infested sites have reduced vegetation density and fewer grasstrees (Xanthorrhoea spp.) that serve as refuge for animals, including the endemic quenda (Isoodon fusciventer). This study investigated whether native CWR mammals face higher predation risks in infested areas. We deployed 40 paired camera traps from April to September 2023 in infested and healthy areas at five peri-urban reserves in Mundaring to record predator and quenda activity. The study sites were professionally mapped for P. cinnamomi, and we performed vegetation assessments at each camera location. We recorded 228 foxes, 7 cats, and 773 quendas, along with several other native CWR mammals. The camera trap data indicate that foxes were 20% more likely to be found in infested areas with reduced vegetative cover (p < 0.005), while nearly 65% of quendas were observed in healthy areas with a higher number of living X. preissii (p = 0.005). The data collected from this project can provide valuable insights for predator management and habitat restoration, helping protect native fauna and their habitats. This research also addresses the knowledge gap regarding the impact of P. cinnamomi on native fauna, which is crucial for informed conservation efforts in the face of this pervasive plant pathogen.

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.