Ascomycetes on Dendroligotrichum (Musci)
Representative herbarium specimens of both species of Dendroligotrichum (Polytrichaceae, Musci) from all parts of the distribution area were analysed for the presence of fungi. Forty collections of the gigantic D. dendroides from southern South America, Juan Fernández Islands, New Zealand and Auckland Islands and 19 of D. squamosum from Fuegia, Falkland Islands and South Georgia were found to be infected by 16 species of ascomycetes. Eleven species occur on D. dendroides, nine on D. squamosum. The species recorded were: Bryochiton heliotropicus, B. perpusillus, Bryomyces sp., Bryonectria disciformis sp. nov., Epibryon elegantissimum, E. eremita, E. interlamellare, E. pulchellum sp. nov., Epibryon spp., Lizonia baldinii subsp. dendroligotrichi subsp. nov., Malvinia endoderma gen. et sp. nov., Potridiscus polymorphus, Potriphila epiphylla sp. nov., and P.navicularis. All species are keyed out, described and most of them are illustrated. Potridiscus polymorphus and Potriphila epiphylla were most frequent. These species occur over the whole geographic range of the host genus. Dispersal of infected host fragments serving as combined diaspore seems to play an important role in parasite distribution. The highly disjunct populations of D. dendroides in South America and New Zealand harbour a more homogeneous set of fungal parasites than D. dendroides and D. squamosum in southern South America. The ascomycetes on D. dendroides presumably reflect the Gondwana origin of their host. A close relationship between D. dendroides and D. squamosum is counterindicated by bryomycological evidence. Dendroligotrichum squamosum and Polytrichadelphus magellanicus which occur sympatrically in Fuegia, have several fungi in common, whereas D. dendroides and P. magellanicus in southern South America and D. dendroides, Dawsonia superba, and P. innovans in New Zealand harbour only specific fungal parasites. With the exception of Lizonia baldinii, the fungal species do not normally cause any visible symptoms on the moss. Individual species show strong preferences for specific sites on the host plants for fruitbody formation. The extremely reduced ascomata of Malvinia endoderma develop within the epidermal leaf cells of D. squamosum. This is a new type of microniche for bryophilous ascomycetes. The present study suggests that populations of Dendroligotrichum are universally colonized by some ascomycetes, though their sporadic occurrence, inconspicuous or concealed form, and the small size of many ascomata and pycnidia render their study rather difficult.