Discriminating among hypotheses of red pigment function in leaves requires knowledge of pigment distribution among taxa and in tissues. I surveyed such pigmentation in 456 species within 98 families, monitored in Miami as well as Costa Rica and Panama. 267/402 of taxa produced anthocyanins in developing and senescent leaves, 57.2 % in development and 21.9 % in senescence. For developing leaves 48 taxa produced pigments exclusively in the epidermis, 105 species in the mesophyll (primarily in palisade cells). For senescent leaves, pigments were in the mesophyll (primarily palisade) for 36 species, versus only 3 species in the epidermis. The 33 species with leaf pigments at maturity (understory and a few floating leaf aquatic taxa) were split between their presence in the lower epidermis versus spongy mesophyll. 5/20 of betacyanin-producing taxa in the Caryophillidae produced pigments in developing leaves, in the epidermis and palisade. These results are not consistent with a general hypothesis of UV protection, and suggest a similar leaf function for anthocyanins and betacyanins--even though the latter absorb little in the UV. Strong representation within the Rosidae (particularly in the Myrtales, primarily in the palisade) and weak representation in the Asteridae suggest an evolutionary influence on this distribution, and a formal analysis by the method of independent contrasts will be completed soon. Pigments also varied between developing and senescing leaves among 37 taxa, indicating considerable developmental plasticity in the expression of anthocyanins.

Key words: Anatomy, anthocyanin, betacyanin, leaf, tropical