urbpan | Weird fungus fact

While researching mushroom-producing fungi for a presentation I did at work, I stumbled upon something unexpected. While most survive either by digesting dead wood, or through a mutualism with tree roots, this one (under the cut) does not.

Underside (spore-producing surface)

This is the ash-tree bolete (Gyrodon or Boletinellus merulioides depending who you consult), and as it's common name implies, it is always found near ash trees. I always assumed that this was because, like many fungi, it lived in association with tree roots (called a "mycorrhizal" relationship, the fungus gets the products of photosynthesis from the tree, the tree gets greater efficiency of its root system).

It turns out that merulioides actually feeds on the honeydew of the ash tree aphid. The insect sucks sap from the ash roots, and produces honeydew as a waste product (ants that "farm" aphids exploit this fact as well), and this is what the fungus survives on.

I have never seen the aphids. They are apparently subterranean, or perhaps they are cryptic; many aphids and their relatives have wooly or scaly disguises and don't look like insects, but rather appear to be a weird texture of the plant they are feeding on. The mushroom is very common where I work, and I have found it in our nearby city parks as well.