XVI International Botanical Congess
Putative eastern North American/temperate Asian disjunct species of macrofungi have been identified in a number of genera. We have investigated morphological and molecular divergence between putative disjunct populations, as well as select circumboreal populations, of species in the genera Sulillus, Xerula, and Laccaria. Species of Xerula are saprobic while the examined species of Suillus and Laccaria form ectomycorrhizas (an obligate mutalism) with certain forest trees, especially species of Pinaceae and Fagaceae. Morphological divergance is undetectable to minimal, and molecular pairs are monophyletic in our analyses. We propose that some of the disjunct pairs are contaxic while others should be treated a separate sister species. Our results are consistent with theory tht these disjuncts are relictual populations of once more broadly distributed taxa that were isolated through recent geological changes including pleistocene glaciation.