A 2006 molecular phylogenetic study of different regional populations of A. muscaria by mycologist József Geml and colleagues found three distinct clades within this species representing , roughly , Eurasian , Eurasian " subalpine " , and North American populations . Specimens belonging to all three clades have been found in Alaska ; this have led to the hypothesis that this was the centre of diversification for this species . The study also looked at four named varieties of the species : var. alba , var. flavivolvata , var. formosa ( including var. guessowii ) , and var. regalis from both areas . All four varieties was found within both the Eurasian and North American clades , evidence that these morphological forms are polymorphisms rather than distinct subspecies or varieties . Further molecular study by Geml and colleagues published in 2008 show that these three genetic groups , plus a fourth associated with oak – hickory – pine forest in the southeastern United States and two more on Santa Cruz Island in California , are delineated from each other enough genetically to be considered separate species ; thus A. muscaria as it stand currently is evidently a species complex . The complex also include at least three other closely related taxa that are currently regarded as species : A. breckonii is a buff @-@ capped mushroom associated with conifers from the Pacific Northwest , and the brown @-@ capped A. gioiosa and A. heterochroma from the Mediterranean Basin and from Sardinia respectively . Both of these last two are found with Eucalyptus and Cistus trees , and it is unclear whether they are native or introduced from Australia .