Variations Within Populations and Classification. Ii. Patterns of Variation Within Asclepiadaceae and Umbelliferae

Summary The very distinct families Umbelliferae and Asclepiadaceae are both represented in western North America. Local samples of the variability within populations and at several ranks in the classification hierarchy were similar in their ranges of variation. The Asclepiadaceae pattern of variability within populations, species, and genera which was revealed with this data base differed only slightly from that obtained previously with a much smaller data base. The quantifications of within‐group variability reveal differences and similarities in patterns of evolution, produce quantifiable models of classification for different families, and can help monographers with taxonomic decisions. A new method of displaying results of intrafamilial patterns of variation uses a log transformation of the CPV and MPD, the summary statistics of the dissimilarity matrices. A comparison of the Umbelliferae, Asclepiadaceae and Bromeliaceae shows the first two to be rather similar in their ranges of intragroup variation at the same ranks and markedly different from the third. The explanation for the similarity between the Asclepiadaceae and Umbelliferae is thought to lie in the coincidence of the general geographic areas where they were sampled and the similarities in their habits: herbaceous, insect pollinated and having umbelliferous inflorescences. The quantifications of infrafamilial patterns of variation clearly show that systematists have tended to mold whatever variation was inherent at the populational level to approximately the same amount of intrageneric variability. Genera in different families seem to encompass very similar amounts of overall variation in spite of differences at the populational level.