What is interesting is that the current way the different varieties of A. muscaria are identified does not hold up to genetic analyses. That means the separation of these varieties based on cap and wart color appears to be incorrect. Instead, genetic analyses indicate there are three distinct clades of A. muscaria and multiple varieties of A. muscaria can be found in one clade. A. muscaria taxonomy based on cap and wort color (i.e. current varieties) will have to be changed. Taken from the discussion section:

'The most parsimonious explanation for the evolution of these morphological varieties is the presence of ancestral polymorphism in pileus and wart colour that pre-dated the separation of the phylogenetic species. In addition, the pileus colour may be influenced by unknown biotic or abiotic environmental factors'.

I never believed in color as a good approach for systematics anyway. That means these 3 clades should actually be considered 3 different species. There is now strong, nearly irrefutable evidence for the separation of the A. muscaria species complex into three different species. They only included a few specimens from CA or other parts of the US besides Alaska, so it is hard to say what is happening in parts of the US.

Based on what they have found elsewhere, there is increasing reason to believe that at least some of the variation in reactions people have to A. muscaria is because different, genetically unique species look so similar.

The different species are likely to have different levels and concentrations of alkaloids and other toxins. Then factor in all the environmental and biological factors, and you've got lots of variability in chemical profiles of the fruit bodies.

I think it's great we finally have the tools to look at things at the (sub)molecular level now. Molecular tools are allowing us to see and understand things we never knew existed. I love DNA.