NUMERICAL TAXONOMIC METHODS, CULTURAL CHARACTERS, AND THE SYSTEMATICSOF ECTOMYCORRHIZAL AGARICS, BOLETES AND GASTEROMYCETES

One hundred and sixty isolates of ectomycorrhizal agarics, boletes, an d related gasteromycetes were examined for 25 morphological and bioche mical characters. A wide range of analytical methods are available wit h which to obtain efficient summaries of the patterns of variation pre sent in data such as these. Agglomerative clustering of 156 isolates a nd 18 characters for which no data were missing resulted in partitions of the sample corresponding to recognizable taxonomic and ecological groupings. Key characters useful for delimiting these groups are highl ighted by means of divisive clustering and classification trees. For e xample, boletes (Boletinus, Suillus, Xerocomus) and related gasteromyc etous allies (Pisolithus, Rhizopogon, Scleroderma) are distinguished b y the production of pigment on media containing high levels of glucose . Numerical taxonomic analyses of cultural characters thus can be usef ul for examining taxonomic relationships, as in the way in which these characters support not only the close relationship between boletes an d some gasteromycetes but also the generic circumscriptions of genera such as Laccaria and Lactarius. However, the taxonomic level at which cultural characters prove most effective must be evaluated carefully, in view of the possibility that, in response to selection, cultural ch aracters have evolved in parallel in separate clades. Thus, ecological as well as taxonomic groups were also recognized. Species of both Heb eloma and Laccaria failed to produce pigment, tolerated low temperatur es, and metabolized urea. This suggests that great care must be taken in using cultural characters in phylogenetic studies.