Assessing biogeographic relationships between North American and Chinese macrofungi

Aim A close biogeographic relationship between the macrofungi of eastern No rth America and eastern Asia has been documented based on comparisons of sp ecies lists. In addition to having a similar species composition, the two r egions are reported to share a number of species with putative disjunct dis tributions. This close biogeographic relationship, however, has rarely been tested within a phylogenetic context. In this paper we examine relationshi ps within three genera, Armillaria, Xerula and Suillus (Fungi, Basidiomycet es, Agaricales) chosen as exemplars of different ecological guilds occupied by macrofungi (plant pathogens, saprobes, mutualists). Location Fieldwork for this project centered in eastern North America, Cent ral America, China and Australasia. Material from additional localities wer e obtained from cooperating herbaria and additional sequences were download ed from GenBank. Methods ITS sequence data were used to construct phylogenies for each genus . Results Only one of four tested putative disjunct species, Xerula hispida H alling and Mueller, was supported. Material referable to X. furfuracea (Pec k) Redhead, Ginns and Shoemaker from China and North America do not form a monophyletic group. Disjunct populations of Suillus spraguei (Berkeley & Cu rtis) Kuntze were shown to be paraphyletic. The morphological similarity of the Chinese material to the North American material is likely due to morph ological stasis. Finally, morphologically identical material referable to S uillus americanus (Peck) Snell in Slipp and Snell from eastern North Americ a and S. sibiricus (Singer) Singer from China, along with the morphological ly similar western North American S. sibiricus, probably represent a single circumboreal taxon. Main conclusions The resulting data, while not refuting the hypothesis that there exists a relatively close biogeographic relationship for macrofungi between eastern North America and eastern Asia, suggest that the relationsh ip may not be as close as indicated by morphological data. These results ar e similar to emerging data from analyses of flowering plants displaying put ative eastern North American/eastern Asian disjunct distribution patterns.