Author: Tao Yun

Publisher:

Published: 1996

Total Pages: 242

ISBN-13:

A three-year field study of aquatic hyphomycete communities in a warm-water stream in Illinois was carried out. Two peaks in total frequencies of aquatic hyphomycetes on randomly collected leaves occurred in each year. In contrast, only a single peak in total conidial concentration in water was observed. While total conidial concentrations in water and total frequencies of the species on leaves in each month were moderately correlated, correlation coefficients between species frequencies on leaves and their conidial concentrations in water in each month were not consistent over time. Species composition and relative frequencies in the communities differed at the same time in successive years, suggesting seasonal influences on community structure. In field experiments with multiple sets of leaf baits overlapping in time, communities on leaves of different submergence periods had similar developmental patterns in total frequencies of aquatic hyphomycetes. Low water temperatures delayed development of communities and compressed peaks of total frequencies of occurrence. At higher temperatures, differences in total frequencies among leaves of different submergence periods were greater. In field studies, higher efficiencies of conidial attachment occurred in species with tetraradiate conidia and higher germination percentages occurred in species with sigmoid conidia. The correlation coefficients for each month between efficiencies of conidial attachment and species frequencies on leaves had a bell-shaped curve over the study period (Feb. to Aug. 1995) when the communities on leaves changed from cold to warm season species. In contrast, the correlation coefficients between germination percentages of conidia and species frequencies on leaves changed in an opposite trend. Laboratory studies on other intrinsic characteristics of the fungi indicated that antagonistic abilities did not seem to be important for colonization of aquatic hyphomycetes on leaves. The differentiations between warm and cold season species in sporulation and mycelial growth on leaves at different temperatures were similar to those present during their seasonal abundance in the field. Some of the aquatic hyphomycetes tested in this study appear to have a ruderal life history strategy on submerged leaves. These results from field and laboratory studies contribute to understanding the ecology of aquatic hyphomycetes in streams.