Charlie: Last week we talked about how our ancestors used (and in some cases abused) mushrooms that had mind-altering compounds in them and that most of these compounds are thought to have evolved to help protect the fungi from being eaten but then, as we got off from the podcast, you mentioned that this wasn’t really the whole story…
Matt: Yeah, I felt bad about that. In the midst of the podcast I lost track of the larger evolutionary tale. It is really complex and there are many elements that we still don’t entirely understand.
Charlie: Hmm...can you give me a summary?
Matt: Sure. So, we explained during the podcast that one possible reason why some fungi are poisonous is to prevent them from being eaten by predators. This may be true for some species but, on the whole, it probably isn’t.
Charlie: Why not?
Matt: Because of the way fungi operate. While we see mushrooms growing out of the ground and assume that what we see is the whole fungus, this is not the case. Most of the fungus is underground forming a thick net to draw nutrients from all sorts of materials. Destroy the mushroom itself and the fungus doesn’t suffer much. The mushroom is only there for reproduction and the fungus can easily grow a new one. Thus, there isn’t much of a reason for a fungus to protect its mushroom with poison.
Charlie: So why are so many fungi poisonous? What is the reasoning?
Matt: We suspect it has to do with protecting the food that they find. While we don’t think about it much, fungi are in fierce competition with a lot of other organisms, like insects and bacteria, that also like to eat the same sorts of foods. By being poisonous and surrounding the stuff that they are eating with their toxins, they are keeping these other organisms from eating their food.
Charlie: That’s cool. It is kind of like they are using their poison to defend their turf. But why are some fungi hallucinogenic?
Matt: Nobody is really sure but there are several theories. One possibility is the one we talked about during the podcast, where giving intelligent animals a bad drug trip teaches them to never come near the fungus again. This is seen all the time with cows and grasses that are being consumed by an aggressive and mind altering fungus. Called “sleepy grass”, once cows eat such tainted food they never go near it again.
Charlie: Interesting. The fungus is playing mind games with the cows to keep them from disturbing it while it eats the grass. I guess the same sort of thing likely happens on the small scale with insects.
Matt: Probably, but no one is sure. I mean, think about it for the moment. It is hard enough to get into the head of a cow and work out that the fungus is causing fear by giving them a bad trip. How the heck would you do that with something like a caterpillar or a beetle?
Charlie: Good point. But what about reindeer? I’ve heard that they actually like to eat mushroom that get them high?
Matt: Again, there is a lot of speculation here. Remember how I mentioned that mushrooms are the reproductive organs for the fungus that is mostly living underground?
Well, while a lot of fungi release their spores into the air, some use the same sorts of tactics that flowers use.
Charlie: What? They lure bees over to them for pollination? Oh wait. No. Reindeer? Are you serious?
Matt: The theory is that reindeer are helping certain fungi to spread their spores. Whether they are spreading them by eating the mushroom and knocking the spores into the air as they do so or are actually digesting the spores and releasing them in their feces is something that still needs to be explore.
Charlie: And they are being rewarded with both a tasty mushroom and a high. Wow.
Matt: It is about more than just not being eaten. It is also about defending your food source…