Cytological Studies in Laccaria (Agaricales). Ii. Assessing Phylogenetic Relationships Among Laccaria, Hydnangium, and Other Agaricales

Laccaria and Hydnangium typically undergo a postmeiotic mitotic nuclear division in basidiospores, basidia, or less commonly, in sterigmata resulting in eight nuclei. Basidiospores formed on tetrasterigmate basidia are binucleate, and those on bisterigmate basidia are tetranucleate in both genera. While Hydnangium and Laccaria likely comprise a monophyletic group—a hypothesis based on a number of shared characters—the presence of multinucleate basidiospores in several putative outgroups precludes using this shared character state as a justification for recognizing these two genera in a separate family, Hydnangiaceae, as had been proposed. Based on a review of the literature, the presence and location of postmeiotic mitotic divisions in basidia and basidiospores of Agaricales do not appear to be appropriate for assessing phylogenetic relationships among genera or families because of a high level of homoplasy.