Three variable characters within the tomato clade have garnered much attention in attempts to understand evolutionary dynamics of the group. The most obvious of these characters is the evolution of carotenoid pigments affecting fruit color. Fruit color of wild tomatoes varies from green to red, orange, and yellow. Various studies have demonstrated that green fruit is the ancestral character and that colored fruit arose once within the clade (e.g., Palmer and Za-mir 1982; Miller and Tanksley 1990; Breto et al. 1993; Alvarez et al. 2001; Marshall et al. 2001; Peralta and Spooner 2001), and their origin is believed to be re cent, about ~1 million years ago (mya) (Nesbitt and Tanksley 2002). The four most derived tomato species bear colored fruit, including the cultivated tomato (S. lycopersicum), S. pimpinellifolium, S. cheesmaniae, and S. galapagense.Within S. cheesmaniae and S. galapagense, fruit color can vary from yellow to deep orange; the other species in the group produce red fruit. Limited levels of genetic variation occur within the tomato clade containing colored fruit, due to its recent origin, which has made resolution of phylogenetic relationships between species difficult. The reason behind a transition to colored fruit in the evolution of the group is unknown, but may be related to seed dispersal.
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