Urban environments harbor greater oomycete and Phytophthora diversity, creating a bridgehead for potential new pathogens to natural ecosystems

Abstract

Anthropogenic activities contribute to changes in the range and distribution of species. Globalization is resulting in human‐mediated dispersal that is causing a breakdown in normal biogeographic barriers. But the impact of anthropogenic activities on plant pathogen communities is still poorly understood. We conducted an eDNA metabarcoding study to compare communities of oomycetes, a group of eukaryotic microorganisms that comprises important crop and tree pathogens, in urban, natural, and interface environments. Oomycete diversity and abundance were highest in human impacted urban environments and lowest in natural environments, while the interface environments were intermediate. Urban environments had the highest proportion of sites where species of the plant pathogenic genus Phytophthora were found, as well as the largest number of unknown or undescribed Phytophthora species. The taxa overlap between urban and interface environments was one order of magnitude larger than the overlap between urban and natural environments. Our analyses show that urban/natural interface areas likely act as a bridge for invasion into natural environments. This could impact both the natural biota and natural ecosystem processes. Our study serves as a warning that some Phytophthora species introduced from nurseries or spread by human movement could pose a threat to natural ecosystems. Shifting patterns in oomycete communities could interfere with natural ecosystem processes and result in increases in disease and ecosystem declines.

Multivariate Bayesian analysis to predict invasiveness ofPhytophthorapathogens

“…It has previously been demonstrated that urban environments and botanical gardens act as a bridgehead for Phytophthora invasions, providing a suitable environment for species to become established and then spread to newly encountered hosts (Hulbert et al, 2019; Paap et al, 2017). The number of species established in natural systems is more limited due to environmental filtering perhaps linked with healthier soils and more resilient environment (Dale et al, 2022; Redondo et al, 2018). The temperature range for mycelial growth and the growth rate at optimal temperature were also important traits influencing tolerance to temperature extremes and ability to rapidly colonize suitable substrate.…”

Oomycete communities are influenced by land use and disease status in Christmas tree production in Southern Québec, Canada

“…were not yet reported or are still regulated species (Anonymous, 2016;Charron et al, 2022;Dale et al, 2022;Feau et al, 2019). However, although the resolution of metabarcoding data is sufficient for many species, care must be taken when inferring the distribution of species belonging to specific clusters or complexes for which the resolution does not allow discrimination between species in the said group or cluster.…”

“…Among the genus of particular interest, 26 clusters or complexes of Phytophthora species were found, confirming the genus's remarkable diversity and ability to adapt to various natural and anthropogenically disturbed environments. However, with 40 species or complexes identified, the genus Pythium was the most diverse, as it is often the case in several natural, urban, and agricultural environments (Cerri et al, 2017;Dale et al, 2022;Fiore-Donno & Bonkowski, 2021;Navarro et al, 2021;Sapp et al, 2019).…”

“…This is the case for species of the G. attrantheridium complex, which were by far the most abundant in this study, in fir plantations or natural forests. G. attrantheridium is a ubiquitous species that predominates in various agricultural (Allain-Boulé et al, 2004;Rojas et al, 2019), urban, and natural environments (Dale et al, 2022;Reinhart et al, 2010).…”

Distribution of Phytophthora species within recreational chestnut, beech and cork oak forests

“…The dispersal of Phytophthora from an initial point of establishment, such as gardens, parks or conservation areas, further into natural forest environments seems to happen through a combination of several factors. Urban environments often function as bridgeheads for invasion by harbouring many exotic species and acting as their first point of contact with the new environment (Dale et al, 2022;Paap et al, 2017). Phytophthora inoculum can be transported in soil, living plants or water.…”