Ecology of nematophagous fungi: Effect of the soil nutrients N,P and K,and seven major metals on distribution

The effects of the major soil nutrients and seven common metals on the distribution of nematophagous fungi were evaluated by comparing the concentration of the elements in soils with and without nematophagous fungi. Mineral nutrients, which were all positively correlated with nematode density, were the most important elements determining the presence of such fungi. Endoparasites producing adhesive conidia were independent of all the elements tested, while those species forming ingested conidia were isolated from soils high in nutrients, indicating a strong dependence on nematode density. Knob forming predators which rely on their ability to spontaneously produce traps to obtain nutrients were isolated from soils with low concentrations of mineral nutrients, while species with constricting rings were isolated from richer soils containing a greater density of nematodes. Net-forming species were largely independent of soil fertility, although generally they were isolated from soils with limited nutrientsd, especially K. Like other fungi, nematophagous fungi are generally not found in soils containing elevated concentrations of heavy metals. The results indicate that even concentrations of heavy metals which naturally occur in Irish soils can restrict the distribution of this fungal group. However the endoparasiteMeria coniospora is tolerant to all metals and to Cu in particular.