Aquatic hyphomycete communities in the river Teign. IV. Twig colonization

Abstract

Corticated and decorticated twigs of alder and oak were placed at five sites along a gradient of stream order and pH in the river Teign, Devon, England. After 2 and 6 months of submersion, twigs were examined directly and then placed individually in bubble chambers to simulate stream conditions. The water was membrane filtered and aquatic hyphomycete conidia on filters were identified and quantified. The mean number of conidia per twig varied from 0 to over 700 000/48 h incubation period and was generally greater from samples at downstream than from upstream sites. Only three species, Heliscus lugdunensis, Mycocentrospora acerina , and Tricladium splendens occurred frequently throughout the river. Longitudinal distribution patterns varied among species with the majority of species occurring from the third site and downstream. Species replacements occurred over time. Species diversity and H' diversity varied among sites and peaked at the penultimate site rather than increasing linearly in a downstream direction. More species of aquatic Hyphomycetes were detected with bubble chamber incubation than with direct examination and moist chamber incubation; the converse was true for Ascomycetes.