Spathulosporales, a New Order and Possible Missing Link Between Laboulbeniales and Pyrenomycetes

SUMMARY

A new order, Spathulosporales, a new family, Spathulosporaceae, and four new species of the genus Spathulospora, parasites on the red algae Ballia callitricha and B. scoparla, are described, and a key to five known species is given. The investigations are based on herbarium material of well-preserved fungi accidentally collected with their host plants 50–120 years ago. Spathulospora adelpha and S. phycophila occur in Australia, S. calva in Australia and possibly New Zealand, and S. lanata in New Zealand, whereas S. antarctica is limited to Antarctic and sub-Antarctic regions. Parasitism and penetration into the host are described. Infection by S. calva induces wild growth of hairs in the host, similar to witches'-brooms. Abnormal fructifications of Spathulospora spp. are depicted and hypotheses for their development are discussed. Members of Spathulosporales are characterized by absence of hyphae; crustose, dark thalli; peg-like penetrating cells; intracellular crusts and stromata; antheridia with spermatia and trichogynes; ostiolate ascocarps without paraphyses; deliquescing asci; and one-celled, appendaged ascospores. The new taxa belong to the Ascomycetes in the Unitunicatae (=Ascohymeniales) and are believed to represent a link between Sphaeriales and Laboulbeniales. Spathulosporales have many features in common with Laboulbeniales, but they differ from them in particular by having a typical pyrenomycetous ascocarp. The taxonomic position of Laboulbeniales is discussed and it is proposed to classify them under Unitunicatae (= Ascohymeniales), close to Spathulosporales. Spathulosporales and Laboulbeniales are considered primitive forms, possibly derived from a common ancestor related to parasitic red algae. Hypotheses on the phylogeny of Ascomycetes are presented and the “primitive Ascomycete” is discussed.