Conidium germination in co-occurring Conidiobolus and Basidiobolus in relation to their ecology

Germination of primary and secondary conidia of 33 strains (12 spp.) of co- occurring Conidiobolus and Basidiobolus from three closely adjacent managed habitats was studied in relation to general nutrient level, water activity of substratrum, light and temperature. A further 26 strains (16 spp.) deri ved from culture collections, and including insect pathogens and saprotroph s, were also compared. Nutrient levels triggering germ-tube formation diffe red widely amongst strains; capilliconidial strains and/or presumptive path ogens usually had a low threshold, Successive generations of globose replic ative conidia formed alternative conidial forms in increasing proportions. Water activity (a(w)) strong influenced development of non-globose conidial forms (microconidia, capilliconidia and actively discharged elongate conid ia). Profiles of response to nutrients, a(w) temperature and light differed between strains (and species) and the comparison represents a first stage in determining niche differentiation, including the putative interactions o f these common fungi with litter invertebrates.