Armillaria is a fungal genus associated with woody plants of diverse ecosystems of North America, South America, Europe, Asia, Africa, and Australia. Species of Armillaria are associated with diverse ecological functions, including root disease pathogens, beneficial decomposers, and beneficial root associates (symbionts) of orchids. Armillaria appears to have co-evolved with woody plants over the last ~100+ million years, which resulted in different species residing in the Northern Hemisphere and Southern Hemisphere. Our collaborative work with scientists from 16 countries focused on DNA-based analyses of Armillaria species from the Northern Hemisphere. Although previous studies indicate that some Armillaria species are present in both North America and Eurasia, our results indicate that some Armillaria species (same taxonomic name) likely represent different species that are associated with diverse regions of the Northern Hemisphere. Thus, Armillaria species from another continent or region may represent an invasive pathogen risk to a region or continent on which Armillaria species with the same name are known to occur. Continued DNA-based taxonomic studies are needed to more accurately assess invasive pathogen risks associated with Armillaria species.
DNA-based phylogenetic analyses identify different Armillaria species in North America (Ross-Davis et al. 2012), (Elías-Román et al. 2013), and other geographic areas (Keča et al. 2015; Ota et al. 2011; Park et al. 2018).
Results indicate that significant genetic variability exists within and among Armillaria species (Klopfenstein et al. 2017). Further taxonomic studies are needed to confirm the existence of distinct species within and among continents that may represent invasive pathogen threats for diverse forest ecosystems across the globe.