Native and invasive populations of the ectomycorrhizal death cap Amanita phalloides are highly sexual but dispersal limited

The ectomycorrhizal death cap Amanita phalloides is native to Europe but invasive in North America. To understand whether the fungus spreads underground using hyphae, or above ground using sexual spores, we mapped and genotyped sporocarps from European and American populations. Larger genetic individuals (genets) would suggest spread mediated by vegetative growth, while many small genets would suggest dispersal mediated by spores. To test whether genets are ephemeral or persistent, we also sampled from the same invasive populations over time. We mapped 13 European and American populations between 2004-2007 and characterized each using amplified fragment length polymorphisms (AFLP). In 2014 and 2015, we resampled populations in California and added three new European populations. These populations and a subset of the specimens originally collected in 2004 were characterized using whole genome sequencing. In every population and across all time points, sporocarps resolve into small, apparently short-lived genets. Sporocarps nearer each other are more closely related, suggesting spores land and germinate near parent sporocarps. A. phalloides uses spores to move across landscapes. Spores travel very short distances and individuals appear ephemeral. The death cap9s life history suggests yearly sporocarp removal as a strategy for control of this deadly fungus.