62 1. The ectomycorrhizal death cap Amanita phalloides is native to Europe but invasive in 63 North America. To understand whether the fungus spreads underground using hyphae, or above 64 ground using sexual spores, we mapped and genotyped sporocarps from European and American 65 populations. Larger genetic individuals (genets) would suggest spread mediated by vegetative 66 growth, while many small genets would suggest dispersal mediated by spores. To test whether 67 genets are ephemeral or persistent, we also sampled from the same invasive populations over 68 time. 69 2. We mapped 13 European and American populations between 2004-2007 and characterized 70 each using amplified fragment length polymorphisms (AFLP). In 2014 and 2015, we resampled 71 populations in California and added three new European populations. These populations and a 72 subset of the specimens originally collected in 2004 were characterized using whole genome 73 sequencing. 74 3. In every population and across all time points, sporocarps resolve into small, apparently 75 short-lived genets. Sporocarps nearer each other are more closely related, suggesting spores land 76 and germinate near parent sporocarps. 77 4. A. phalloides uses spores to move across landscapes. Spores travel very short distances 78 and individuals appear ephemeral. The death cap's life history suggests yearly sporocarp 79 removal as a strategy for control of this deadly fungus. 80 81 82 83 84 85 86 87 88 89 90 91 92 invading on its own is likely to have an invasion dynamic distinct from a fungus associating with 108 an invasive plant (Dickie et al. 2017). However data tracking ECM invasions are limited, as are 109data describing potential impacts. Open questions include whether these fungi persist as 110