[contingo]

As the article hints, the concept of an individual is a very slippery thing in filamentous fungi. A single hyphal network can contain genetic material from more than two parental spores, and while a bi-nucleate condition is typical (in a "stable dikaryon"), genetically different nuclei can cohabit different regions of the same mycelium at different times, and even established nucleotypes can be completely displaced by newly-fusing types. This all leads to quite different genetic situations from those that delimit individuals in the usual sense.

In this study, somatic compatibility of isolates (their readiness to fuse into a single mycelium) seems to have been interpreted as an indication of clonality – that the isolates are completely genetically identical. (At least it was by the BBC; the abstract of the linked paper, which is all I read of it, is vague on this point.) That would make the determination that this is a single individual fungus rather unassailable. But it's not clear to me at all that we can assume things are so simple.