Par Baral H.-O.
Vol. 15 (1) – 13 avril 2023
Seulement pour les abonnés
Résumé (anglais) : Agyrium roseum is described based on four collections on felled, decorticated logs of Picea abies and Pinus sylvestris in a colline mixed beech forest in the cold-temperate nature reserve Schönbuch in Tübingen (Germany). Two further collections were made on old standing Picea abies stumps in the montane, orotemperate Šumava Mountains (Czechia). The species is characterized by small, erumpent apothecia with a light purple-rose disc, and living ascospores containing regularly two large lipid bodies and a few small ones. A description of A. rufum is provided for comparison, based on three collections from montane central and southern and from boreal northern Europe. A. rufum differs from A. roseum in larger, bright orange apothecia, wider asci, and wider ascospores with a higher lipid content which is never consistently biguttulate but varies between many small LBs (multiguttulate) and one, rarely two large and many smaller and minute LBs. Both species occur gregariously on exposed, xeric, decorticated coniferous wood and provoke a whitish, bleached appearance of the wood surface that resembles a thallus, though without a definitive symbiosis with algae. Judging from the very sparsely available sequences in GenBank, A. rufum on coniferous hosts could be a complex of two different species, one occurring in warm-temperate North America and one in boreal North America and Europe. Several literature reports of angiosperms as host of A. rufum require reexamination and DNA studies. Only two further species are currently accepted in the genus: A. aurantium on Rhododendron from China and A. antarcticum on Nothofagus from Chile, both lacking DNA data. During the present study, DNA was obtained from apothecia of A. roseum from South Germany (ITS, LSU) and Bohemia (ITS, mtSSU), supporting a close relationship with A. rufum, with a p-distance of 5.3–6% in the ITS region, 3.5–4% in the LSU D1–D2 domain, and 1.2–1.9% in the mtSSU.
During screening of felled decorticated conifer logs for Symbiotaphrina (≡ Tromeropsis) microtheca in the forests around Tübingen, two collections of a seemingly non-lichenized agyrium-like fungus with light purple-rose apothecia growing on whitish areas on otherwise greyed, naked wood of Pinus and Picea were made[…]