[hristov]

The fly agaric, is very poisonous and has a very distinctive red with white dots pattern to warn about its poison. Unfortunately, that pattern looks so pretty that disney and ninetendo decided to use it as their generic mushroom coloring. So, if you are hiking with your kids, and they see a pretty mushroom just like in cartoons, don't let them touch it.

If there are enough poisonous mushrooms, it is possible that most animals decide to leave mushrooms alone regardless of distinctive coloring. That seems to be the case because mushrooms tend not to be bitten by large animals, at least when i go mushrooming. If that happens, it is possible that other mushrooms do not develop poison but rather freeload on the poison of other mushrooms.

Thus, one may guess, that first distinctive poisonous mushrooms like the fly agaric developed, then most animals large enough to eat them developed an instinct to avoid all mushrooms, and then the non-poisonous freeloading mushrooms developed.

There are some psychedelic mushrooms in the amazon that use their psychedelic effect to zombify ants and force them to spread the mushrooms spores. That is really disturbing, find a youtube video of it if you feel like having some nightmares.

Furthermore it should be noted that the poison or the psychedelic effect may not even be relevant for evolution. The poisonous or psychedelic compound may be produced for completely different purpose or as a byproduct of the production of another useful compound.

[vintermann]

There are plenty of poisonous plants that large animals e.g. farm animals will happily eat and die. Yew, water hemlock etc. are notorious livestock killers.

According to a farmer friend of mine, sheep are also absolutely crazy about hedgehog mushrooms (hydnum repandum), which is not poisonous, but it suggests that they don't shun mushrooms.

[uplifter]

>Thus, one may guess, that first distinctive poisonous mushrooms like the fly agaric developed, then most animals large enough to eat them developed an instinct to avoid all mushrooms, and then the non-poisonous freeloading mushrooms developed.

Just wanted to note that these phenomena are important enough in the study of mimicry in biology to have earned their own names:

Müllerian mimicry is when two species who are similarly well defended (foul tasting, toxic or otherwise noxious to eat) converge in appearance to mimic each other's honest warning signals.

Batesian mimicry is when a harmless or palatable species evolves to mimic a harmful, toxic, or otherwise defended species.