Alternative extreme models of cox1 intron evolution in Solanoideae. Presence of the intron is indicated by red branches, names in red boldface, and red plus (+) symbols. Black lines and minus (-) symbols show intron-lacking taxa. Numbers to the left of plant names give the minimum estimated size of the 3' CCT (question marks indicate that exons were not sequenced). Intron gain is marked by a filled red rectangle, while intron and CCT loss are marked by a black "X". A) Single intron gain in Solanoideae, followed by multiple losses of the intron and CCT. B) Two intron gains in Solanoideae, with no intron or CCT losses. The double-headed arrow indicates a possible within-Solanaceae horizontal transfer of the intron.