The effects of dictyostelids on the formation and maturation of myxomycete plasmodia.

Dictyostelids (cellular slime molds) and myxomycetes (plasmodial slime molds) are two groups of mycetozoans usually present and often abundant in the soil and litter microhabitats of terrestrial ecosystems. Because they utilize the same food resource and occur together in a spatially limited and clearly defined microhabitat, the potential for ecological interactions would seem to exist. However, relatively few previous studies have considered this aspect of mycetozoan ecology. In the present study twenty-eight isolates (8 species) of dictyostelids were co-cultured in all possible pair-wise combinations with fourteen isolates (7 species) of myxomycetes to determine if there were any effects on the production of fruiting bodies. Dictyostelids showed little or no delay in culmination and only random and inconsistent reductions in sorocarp abundance when co-cultured with myxomycetes. In contrast, myxomycetes displayed a number of specific effects. The heterothallic isolates exhibited delays in plasmodial formation and/or maturation, with some pairings showing little to no effect, while others displayed nearly complete inhibition of plasmodial formation or maturation. Apomictic isolates, in general, were much less affected, with only a few combinations displaying significant delays in both formation and maturation of plasmodia.