| Chapter 1. Cyttaria species are obligate, biotrophic associates of species belonging to Nothofagus, the southern beech. As such, they are restricted to the Southern Hemisphere, inhabiting southern South America and southeastern Australasia. Phylogenetic analyses based upon molecular and morphological data define Cyttaria as a strongly supported monophyletic group and provide limited evidence for a close relationship between Cyttaria and certain diverse members of the Leotiomycetes. Twelve Cyttaria species are recognized, including one known in New Zealand by the misapplied name C. gunnii. Three major clades are identified within Cyttaria : one in South America on subgenus Nothofagus, another in South America on subgenera Nothofagus and Lophozonia , and a third in South America and Australasia on subgenus Lophozonia.;Chapter 2. The association between species belonging to Cyttaria and their hosts, the species of Nothofagus subgenera Lophozonia and Nothofagus, is often cited as a classic example of cophylogeny. Cophylogenetic analyses based upon molecular and morphological data indicate that Cyttaria species exhibit highly significant cophylogeny with their hosts. Two major lineages of Cyttaria are each confined to a single Nothofagus subgenus, a specificity that accounts for a minimum of two codivergence events in this system. Given the historical association of Cyttaria and Nothofagus, the results may support the vicariance hypothesis for the trans-Antarctic distribution between Australasian and South American species of Cyttaria species hosted by subgenus Lophozonia. They also support the hypothesis of transoceanic long distance dispersal to account for the relatively recent relationship between Australian and New Zealand Cyttaria species.;Chapter 3. Chorioactis geaster exhibits an unusual geographical disjunction, with populations known only from Texas, USA and Kyushu, Japan. Phylogenetic analyses based upon molecular sequence data are used to infer the phylogenetic and biogeographic history of this fungus. The results suggest distinct American and Japanese lineages and support the hypothesis that a dematiaceous hyphomycete, Conoplea aff. elegantula , is an anamorph of Ch. geaster. Using a molecular clock, the divergence between the two Ch. geaster lineages is estimated to have occurred at least 19 mya. Despite the pronounced temporal, geographical, and molecular disjunction, the two lineages exhibit a remarkable degree of morphological stasis. |
