Mycorrhizal networks which allow carbon compounds and mineral nutrient
s to be passed between individual plants, even members of different sp
ecies, are potentially of great ecological importance. The evolution o
f such systems is of particular interest as they appear to need a grou
p selectionist explanation. I suggest that such explanations are not n
ecessary to explain the evolution of these systems as gene level expla
nations can be provided which appear to be sufficient to explain their
evolution. Such explanations are to be preferred since they are less
open to problems with cheating by the symbionts and therefore more sta
ble.