Epiphytic and fimicolous myxomycetes on the island Hiddensee (Germany): rare species, new genotypes and unexpected ecological preferences

Abstract

Hiddensee, a small island in the Baltic Sea, is characterized by a rather dry, windy, and sunny climate, resembling a periodic desert. We studied epiphytic and fimicolous myxomycetes on the island using the moist chamber method for 101 substrate samples. A total of 37 myxomycete species were identified from 124 records, including 4 species newly recorded in Germany. Molecular barcoding revealed that 67 % of the obtained DNA sequences were new, differing by more than 1 % from their closest matches in the GenBank database. We obtained the first molecular data for Didymium megalosporum (found to be related to the aethaloid species D. spongiosum and D. yulii) and C. elegans var. microspora (new data for both the species and the variety). For Trichia rapa, described in 2023 based on a single barcoded collection, we found three different ribotypes, including one already known. Presumably undescribed taxa within the morphospecies Comatricha nigra, Didymium squamulosum, Enerthenema papillatum, and Trichia contorta were identified by molecular barcoding. Substrate preferences of myxomycetes, categorized into four substrate types (bark of living trees, leaf litter, twigs, and dung), showed distinct patterns of occurrence, with each substrate type associated with a characteristic assemblage of myxomycetes. The species composition on the bark of living trees showed a well-known dependence on bark pH and hardness, with differing pH optima and tolerance ranges among the studied species. Echinostelium minutum occurred across a broad pH spectrum (6.1–8.0; 11 records), whereas Didymium leptotrichum was restricted to a narrow pH range (7.9–8.1; 7 records). Trichia munda preferred relatively acidic substrates (6.4–7.2; 9 records), while Perichaena luteola (7.4–8.0, 5 records) was more commonly found in slightly alkaline conditions.