Gringoes bajo el bosque: Coinvasions by ectomycorrhizal fungi and Pinaceae species in Patagonia

Background/Question/Methods              Biological invasions by members of the family Pinaceae occuring far from their native range take the form of coinvasions with obligate ectomycorrhizal (EM) symbiotic fungi. These fungi and their autotrophic symbionts disperse independently, and frequently via different vectors, potentially giving rise to reciprocal codispersal limitations. Using two field sites in Patagonia, we asked three questions: first, do invasive mammals disperse EM fungal propagules? Second, is there a minimum EM fungal species richness required to trigger an invasion? And third, how are EM fungal communities in a coinvasive context structured? We used a bait-plant method to assess fungal inoculum in non-native mammal feces. We also completed extensive belowground sampling of coinvasive EM fungal communities near Coyhaique, Chile and on Isla Victoria, Rio Negro Province, Argentina.

Results/Conclusions      We report that EM fungi are transported by invasive wild boar and deer and that a single fungal species can trigger a Pinaceae invasion. We also report that several of the coinvasive fungi we detected in Patagonia appear to be key players in coinvasions elsewhere; we argue that at least one of these species, Suillus luteus, meets the formal definition of a keystone species. Finally, we discuss factors, including codispersal limitation, that structure EM fungal communities and permit Pinaceae-EM fungal coinvasions.