Patterns of Occurrence of Ascomycetes Associated with Decomposing Twigs in a Midwestern Stream

ABSTRACT

Packs of twigs from cherry, oak, silver maple, and sycamore trees were placed in an Illinois stream and samples were recovered periodically over 30 months. Ash-free dry weights remaining over time were determined and twigs were examined for Ascomycetes directly and after incubation. Twigs disappeared at rates much lower than those reported for leaves and provided an enduring substrata for fungi. Thirty-three Ascomycetes were collected: Pseudohalonectria lignicola and Savoryella lignicola are reported from the United States for the first time. Nectria lucidum, Pseudohalonectria lignicola, Leptosphaeria sp. 1, and Aniptodera sp. 1 occurred most frequently. With the exception of the decline of blastocladiaceous and saprolegniaceous species after one week, and the disappearance of N. lucidum after the first year, distinct changes in community structure did not occur during the submersion period. Generally, the numbers of species and the frequencies of occurrence of predominant species increased with increased time of submergence. Long-term incubation of substrata yielded the greatest number of Ascomycetes: incubation in light/dark conditions increased the number of species and the frequencies of occurrence of individual species over dark incubation.

Key Words:

• aquatic ascomycete
• wood decomposition
• succession