Phylogenetic relationships and species richness of coprophilous ascomycetes

University dissertation from Umeå : Ekologi, miljö och geovetenskap

Abstract: Coprophilous ascomycetes are a diverse group of saprobes, of which many belong to three families, Delitschiaceae, Phaeotrichaceae and Sporormiaceae, within the large order Pleosporales. The natural relationships and circumscription of these families are unclear, especially within the family Sporormiaceae, where the generic delimitation have been questioned. There is also a need to understand how different ecological processes affect species richness and occurrence of coprophilous ascomycetes in general. The aim of this thesis was therefore to test earlier classifications of coprophilous taxa within Pleosporales, using phylogenetic analyses of DNA sequences; and to study how the habitat, dung type and herbivores´ food choice may affect the species richness and species composition of coprophilous ascomycetes.A phylogenetic study shows that coprophilous taxa have arisen several times within Pleosporales. Sporormiaceae and Delitschiaceae are separate monophyletic groups and should continue to be recognized as two distinct families within Pleosporales. Phaeotrichaceae forms a monophyletic group, and is, unexpectedly, a strongly supported sister-group to Venturiaceae, but if they belong to Pleosporales or not, remains unresolved. Testudinaceae and Zopfiaceae, which previously had an unclear position in Ascomycota, are shown to be members of Pleosporales and should be treated as two separate families. The genus Eremodothis is, however, not related to Testudinaceae, but is nested within Sporormiaceae and should be transferred to Westerdykella.The natural relationships within Sporormiaceae are still not fully resolved and consequently, I suggest a rather conservative generic classification, accepting Preussia, Sporormia, Westerdykella, as well as Sporormiella, despite that the latter is not conclusively well supported as monophyletic. Characters previously used in the taxonomy and classification of Sporormiaceae, as choice of substrate, presence or absence of an ostiole, presence or absence of germ slits, and spore ornamentation, were all homoplastic and not very useful for circumscribing monophyletic groups.Field-studies of moose (Alces alces), mountain hare (Lepus timidus) and roe deer (Capreolus capreolus) dung resulted in several new species records, which suggests that coprophilous ascomycetes in boreal Sweden are poorly known. Fungal species richness and occurrence on moose dung varied significantly between habitats. Species diversity was negatively associated with amount of insect attack, and insects feeding either on the dung and/or the fungi may be an important factor explaining the observed pattern. Species richness of coprophilous fungi varied also significantly between different dung types. A study of moose, mountain hare, and roe deer dung did not show any consistent patterns in respect to the animals´ digestive system. There was, however, a general strong positive relationship between the total number of ascomycete species and the number of plant species foraged by the three herbivores. Fungal species with large spores (≥ 50 µm) were over-represented on roe deer dung, and under-represented on moose dung, while the reverse was found for species with small spores (<10µm). This suggests that the foraging level of the herbivore, which in turn mirrors species-specific differences in spore dispersal of the fungi, may be an important factor in explaining species richness and diversity of the coprophilous community.

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