Sunday, July 4, 2010

Mushroom of the Month, July 2010

Quite a rare find, Boletus parasiticus (synonym: Pseudoboletus parasiticus) is commonly referred to as the parasitic bolete. It is always found with common earthballs, Scleroderma citrinum. That seems to suggest that this bolete consumes the earthball to which it appears to be attached, and yet some scientists are now suggesting that the relationship may not be parasitic after all. Well, perhaps so, but I remain to be convinced: just look at how the earthball in the picture above appears deflated, as though something is consuming its innards.

There seems to be little dount that Boletus parasiticus cannot live without its earthball associate, and every specimen that I find is with an earthball partner. Often a single earthball is 'host' (if that is an appropriate term for the true relationship between these two fungi) to several fruitbodies of the parasitic bolete. Parasitic boletes are hard to find, and stumbling across a patch of common earthballs is no guarantee that you are about to see this rather dull and unimpressive member of the family Boletaceae: most earthballs occur without parasitic boletes.

If you ever go across the sea to Ireland, as the song says... some way south of Galway bay is the lovely town of Killarney and its nearby lakes and mountains. Within the woodland there, and most particularly near Mucross Abbey, common earthballs line many of the drainage ditches, and quite a high proportion of those earthballs have parasitic boletes attached to them.

Where else is good? Well. my favourite hunting ground is in the narrow strip of woodland along the gorge of the River Teifi at Henllan, in West Wales. There, every year, while hunting rare fungi and lichen I come across dozens of parasitic boletes with, of course, common earthballs.

I have looked out for these intriguing boletes in so many other places and failed. The New Forest, in southern England; the Caledonian Forest, in Scotland; the Forest of Dean, in the Wye Valley; numerous pinewoods in France, Portugal, Bulgaria... But of course, not finding them doesn't mean that they are not there. These are fairly inconspicuous fungi, almost always in deeply shaded habitats with plenty of leaf litter, with which backgrounds they blend in very well.

One final point... this is always a woodland mushroom, as indeed are most if not all other boletes. The common earthball, Scleroderma citrinum, is ectomycorrhizal with both hardwood and softwood trees (broadleaves and conifers), meaning that it lives in a mutually beneficial relationship (termed symbiosis) with the fine rootlets at the ends of the roots of trees. The fungus in effect feeds the tree and the tree also delivers vital chemicals to the fungus. Meanwhile, within this ménage à trois, the parasitic bolete is also up to something, and I suspect it is up to no good! How often we find that these interrelationships between fungi and plants are far from simple. For example the rare wild orchid Limodorum abortivum is now known to depend on certain kinds of Russula fungi which themselves require pine trees - explaining why the violet limodore, to quote the orchid's common name, is found only beneath pine trees.

We certainly do live in an amazing (and amazingly complex) world.

Do let me know if you are able to add to (or correct) any of the above...

Happy hunting!