Diversity of xylariaceous symbionts in Xiphydria woodwasps: role of vector and a host tree

Siricid woodwasps live in obligatory nutritional symbiosis with fungi. Screening of symbionts from mycetangia of emerging Xiphydria females (X. longicollis, X. prolongata, X. camelus, X. picta) from 28 locations and four tree genera yielded 1 389 isolates. Each female carried a pure culture of a single fungus. In X. longicollis (Quercus), Daldinia childiae was either the only fungus or a highly dominant one in the samples from moderately dry oak-hornbeam (Quercus–Carpinus betula) forests. Females from the alluvial sites harboured D. childiae and Daldinia decipiens (approx. 1:1). X. camelus and X. picta (Alnus) shared the dominant symbiont D. decipiens whereas X. camelus from Betula carried D. decipiens and D. petriniae (approx. 1:1). In X. prolongata, D. childiae was the dominant species followed by an undescribed Daldinia sp. (0–20 % of isolates); D. decipiens was rare and in three females Hypoxylon macrocarpum was found. No symbiont occurred in a significant number among endophytes from the host trees.