An immunological comparison of the Sciadopityaceae, Taxodiaceae, and Cupressaceae

Seed protein extracts were compared by radioimmunoassay to assess relationships among genera of the traditional Taxodiaceae and Cupressaceae and their position relative to the other conifer families. Immunological distance data indicate that the Cupressaceae and Taxodiaceae form a distinct lineage, of which the Cupressaceae s. str. is a monophyletic subset. Subgroups of the Taxodiaceae are at least as distant from one another as they are from the Cupressaceae, supporting Eckenwalder's proposal to merge the two families. The morphologically anomalous genus Sciadopitys, often assigned to the Taxodiaceae, is as distant immunologically from the taxodiaceous genera as it is from the other families of conifers, supporting its treatment as the monotypic family Sciadopityaceae. Phylogenetic interpretation of morphological data generally accords well with the immunological analysis, but indicates that Sciadopitys is the closest extant relative of the cupressaceoustaxodiaceous lineage.