Climate Change Projected to Double the Richness and Abundance of Soilborne Phytopathogenic Fungi in Southern Maritime Antarctica.

How climate change impacts pathogens in the natural environment is a critical ecological question. Yet, little is known of how rapid ongoing climate change in Antarctica and Patagonia will influence the fungal pathogens in the barren soils typical of these regions. Here, using DNA metabarcoding and LASSO regression, we identify climatic factors-and notably mean annual air temperature-as the best predictors for the taxonomic richness and relative abundance of fungal pathogens of plants and animals in barren soils sampled from along a 1900-km transect through sub- and Maritime Antarctica and Patagonia. Projected changes to climate under three shared socioeconomic pathway scenarios (SSP1-2.6, SSP3-7.0, and SSP5-8.5) were used to predict how soilborne pathogenic fungal communities will alter by 2071-2100. The SSP3-7.0 and SSP5-8.5 scenarios were projected to cause approximate doublings to the richness and abundance of phytopathogenic fungi in southern Maritime Antarctic soils. Weaker effects of these two scenarios were found on phytopathogens elsewhere on the transect and on animal pathogenic fungi. Changes to climate under the SSP1-2.6 scenario had negligible impacts on both guilds. Edaphic factors explained lower amounts of variance in soil pathogenic fungal diversity and relative abundance than climatic factors. Our findings indicate higher frequencies of fungi causing grey molds, stem necroses, blights, scabs and leaf spots in warmer soils. They foreshadow end-of-century increases in the richness and abundance of phytopathogenic fungi inhabiting the barren soils of southern Maritime Antarctica, posing a threat to the region's flora as it colonizes these soils.