Person:

Pfister, Donald

The obligate, biotrophic association among species of the fungal genus Cyttaria and their hosts in the plant genus Nothofagus often is cited as a classic example of cophylogeny and is one of the few cases in which the biogeography of a fungus is commonly mentioned or included in biogeographic analyses. In this study molecular and morphological data are used to examine hypotheses regarding the cophylogeny and biogeography of the 12 species of Cyttaria and their hosts, the 11 species of Nothofagus subgenera Lophozonia and Nothofagus. Our results indicate highly significant overall cophylogenetic structure, despite the fact that the associations between species of Cyttaria and Nothofagus usually do not correspond in a simple one to one relationship. Two major lineages of Cyttaria are confined to a single Nothofagus subgenus, a specificity that might account for a minimum of two codivergences. We hypothesize other major codivergences. Numerous extinction also are assumed, as are an independent parasite divergence followed by host switching to account for C. berteroi. Considering the historical association of Cyttaria and Nothofagus, our hypothesis may support the vicariance hypothesis for the trans-Antarctic distribution between Australasian and South American species of Cyttaria species hosted by subgenus Lophozonia. It also supports the hypothesis of transoceanic long distance dispersal to account for the relatively recent relationship between Australian and New Zealand Cyttaria species, which we estimate to have occurred 44.6–28.5 mya. Thus the history of these organisms is not only a reflection of the breakup of Gondwana but also of other events that have contributed to the distributions of many other southern hemisphere plants and fungi.

Angelina rufescens is placed within the core clade of Rhytismatales (Leotiomycetes, Pezizomycotina, Ascomycota) based on analysis of LSU and mtSSU rDNA. The only species in the genus, it produces distinctive ascomata that reoccur annually on wood and on the remains of its own previous fructifications, forming dense conglomerations of interlocking longitudinally elongated apothecia with gray hymenia. Known collections and references of A. rufescens indicate that it is endemic to eastern and central United States. Morphological and cultural characters are described with notes on ascomata development. No mitospores were observed in field collections or in culture. Lectotypes are designated for Hysterium rufescens and its synonym Ascobolus conglomeratus. Angelina rufescens is illustrated here for the first time in the taxonomic literature.

Medeolaria farlowii, an ascomycetous parasite of Medeola virginiana, has been included as the only member of the family Medeolariaceae and order Medeolariales. Its assignment within the Ascomycota has been problematic due to the lack of distinctive ascomatal form and ascus morphology. Asci are formed in a loosely organized hymenium on hypertrophic portions of Medeola virginiana stems. Phylogenetic analyses of nuclear 5.8S, large subunit, and small subunit rDNA gene sequences place M. farlowii in the Leotiomycetes with parsimony, Bayesian, and maximum likelihood analyses, but its position within this class remains unresolved. In general, limited taxon and gene sampling in the Leotiomycetes hampers placement of taxa within this class. A survey of available sequence data in the Leotiomycetes is given, and the implication for phylogenetic studies within the class is discussed. Medeolaria farlowii should be treated as a monotypic genus in the monotypic order Medeolariales, class Leotiomycetes.