Functional complementarity in the arbuscular mycorrhizal symbiosis

The causes and consequences of biodiversity are central themes in ecology. Perhaps one reason for much of the current interest in biodiversity is the belief that the loss of species (by extinction) or their gain (by invasion) will significantly influence ecosystem function. Arbuscular mycorrhizal (A M) fungi are components of most terrestrial ecosystems and, while many rese arch programs have shown that variability among species or isolates of An f ungi does occur (Giovannetti & Gianinazzi-Pearson, 1994), the basis for thi s variability and its consequences to the function of communities and ecosy stems remains largely unexplored. Smith et nl. (pp. 357-366 in this issue) non show clearly that ecologically significant functional diversity exists among AM fungal species in the regions of the soil from which they absorb p hosphate, and their results suggest that such diversity may have significan t ecological consequences.