Phylogenetics and host distribution of Armillaria in riparian ecosystems of the northern Great Plains

Root disease pathogens, including Armillaria (Fr.) Staude, are a leading cause of growth loss and mortality of trees in forest ecosystems of North America (Lockman & Kearns 2016). This panglobal fungus can cause significant reductions in tree growth that can lead to mortality. Armillaria spp. have a wide host range, and they also play a vital ecological role in the carbon cycling process via wood decomposition (Raabe 1962, Baumgartner et al. 2011, Heinzelmann et al. 2019). As a native root-disease fungus, Armillaria spp. are among the oldest and largest known living organisms on Earth (Ferguson et al. 2003). Armillaria root disease has been found in every region of the United States. Currently, 11 species of Armillaria/Desarmillaria are known to occur in North America (Kim et al. 2006, Klopfenstein et al. 2017, Elías-Román et al. 2018), each with different ecological roles from pathogenic to saprophytic. Very little work has been done identifying and characterizing the distribution of Armillaria spp. in the northern Great Plains region, although A. gallica Marxm. & Romagn was previously identified in association with diverse hardwood species in the Niobrara Valley Preserve in Nebraska (Kim & Klopfenstein 2011).