The Evolution of Fruit Color in Fleshy-Fruited Plants

Abstract

Red and black are the most common colors of bird-dispersed fruits in all regions of the world for which information is available; other colors occur, but at lower frequencies. We present 13 nonexclusive hypotheses that may contribute to the observed frequency distribution of fruit colors and assess them, in a preliminary way, using existing information. Five hypotheses relate fruit colors directly to avian foraging: (1) birds prefer red and black (weak support at best); (2) red and black displays are more readily discovered by foraging birds (mixed evidence); (3) fruit colors indicate fruit maturity (mixed evidence); (4) fruit colors facilitate quick recognition of food (little evidence); (5) nutritionally poor fruits mimic nutrient-rich fruits (no data). Three hypotheses relate fruit colors to defense against natural enemies: (6) red fruits are inconspicuous to fruit-foraging arthropods (limited applicability); (7) fruit colors exclude poor dispersal agents (few data); (8) fruit pigments defend fruits against parasites and pathogens (no data for present day fruits; may have been important in evolutionary time). In addition, fruit colors may be physiological adaptations (hypothesis 9; little evidence) or may have evolved by selection acting on correlated characters (hypothesis 10; few data). Finally, production of fruit pigments may be constrained by metabolic costs (hypothesis 11; few data), by competition for dispersal agents (hypothesis 12; no data), or by phylogenetic history (hypothesis 13; little support). We draw together a large body of information from various sources in our preliminary assessment of these hypotheses, but there is no substitute for direct experimentation and comparison.