Anthocyanins have been intensely studied because of their expression in flowers and fruits of economic importance, yet they are also produced in vegetative organs, even in plants preceding the evolution of angiosperms. There has been much speculation on the function of this coloration, particularly by the physiological anatomists of the 19th century, but little serious research. A pre-condition to research on their function is a thorough knowledge of anthocyanin patterns in leaf tissue and their distribution among vascular plants. In a survey of 463 tropical taxa these patterns were investigated; tissue distributions in 399 taxa were mapped on the robust three-gene molecular phylogeny of Soltis et al. (Nature 402:402-404), pruned for these taxa with additional structure from other studies. Incidence and patterns of anthocyanin production were strongly associated with certain families, notably the Myrtaceae and Combretaceae, and were poorly represented among the Asteridae. Statistical analysis indicated that certain tissue distributions were significantly influenced by phylogenetic drift, despite many unresolved polytomies below the family level. Anthocyanin production in other plant parts was significantly associated with that in leaves in this sample of taxa. Most tissue patterns were limited to mesophyll tissue, and a smaller number limited to epidermal layers. The rarity of tissue combinations combining both germ lines (dermal and ground) suggests strong developmental constraints on locations of anthocyanin production in leaves. Only 13.5 % of these taxa produced anthocyanins during senescence, contrasting strongly with a high 70 % of 91 taxa sampled during senescence at Harvard Forest, in central Massachusetts. Similar patterns of betacyanin distribution were observed in a smaller sample of 21 taxa in the Caryophyllales. Similarities in absorbance spectra in visible wavelengths and strong in vitro anti-oxidant activities suggest that these two pigments may have similar physiological functions in leaves.

Key words: anatomy, angiosperms, anthocyanins, development, leaf, phylogeny