Relationship between phylogenetic distance and chemical diversity (number of alkaloid group differences) for Amaryllidaceae subfamily Amaryllidoidae. A) Scatter plot showing distribution of points and best-fit regression line. The size of each point is proportional to the log-transformed number of data points contributing to it. B) The same data showing mean (±s.e.) number of differences for categories of phylogenetic distance (number of substitutions per site) for ease of visualization. The overall relationship is significant. There is a statistically highly significant correlation between differences in chemical profile and phylogenetic distance, although the effect is not strong (Mantel test: r = 0.085, p = 0.002), indicating that closely related species tend to have more similar chemical profiles than more distantly related species.