Mueller, Gregory , Hosaka, Kentaro .
Host specificity versus geology in shaping biogeographic patterns of ectomycorrhizal fungi.
Until relatively recently, the accepted paradigm was that most fungi were broadly distributed due to the high dispersal potential of their spores. A corollary of this view was that little attention has been paid to fungal biogeography. Broad geographic and taxonomic sampling as part of modern inventory and systematic studies documented the presence of discrete communities of fungi in different geographical regions. Recent phylogenetic studies have both uncovered “cryptic” species and provided the framework to assess phylogeographic patterns and hypothesize about processes responsible for these patterns. Ectomycorrhizal fungi (i.e., those fungi obligately associated with the roots of certain groups of plants) show discrete distribution patterns and high levels of endemism. In most cases, there is a stronger geographic than host association component to the observed distribution patterns. So while many species of ectomycorrhizal fungi show at least some host preference, these taxa are nested within clades denoted by geography that contain taxa associated with various hosts. For example, most Australian species of Laccaria and Hysterangiales associate with either Eucalyptus or Nothofagus, not both, but they are interspersed on our multigene phylogenetic trees. These phylogenetic analyses are useful in assessing the relative role of vicariance events versus dispersal for explaining current distribution patterns. While a Gondwanan origin has been identified in several well-studied clades of ectomycorrhizal fungi, dispersal and subsequent radiations are responsible for current distribution patterns in these taxa. Our very preliminary data for Cantharellales, a basal clade of the Agaricomycetes, do not recover an austral group of taxa. It is unclear if this is due to a different evolutionary history or due to insufficient sampling. In any case, it is becoming clear that the biogeography of ectomycorrhizal fungi is due more to geographic history than to host association.
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1 - Field Museum of Natural History, Botany, 1400 South Lake Shore Drive, Chicago, Illinois, 60605, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Boulevard A/Hilton
Date: Tuesday, July 10th, 2007
Time: 1:30 PM