THE ROLES OF ONTOGENIC EVOLUTION IN THE ORIGINS OF FLORAL HOMOPLASIES

Homoplasy, manifest as convergence, parallelism, or reversal, is an im portant aspect of floral diversity. Few studies have focused on the ev olution of floral homoplasies, and the role of ontogenetic evolution i n their origins has been largely ignored. Four clades of angiosperms, the genera Besseya (Scrophulariaceae) and Eucnide (Loasaceae), the fam ily Hydrangeaceae, and the order Piperales, were used to examine the r oles of ontogenetic evolution in creating floral homoplasies. The poss ible modes of ontogenetic evolution were found to contribute unequally to the origin of homoplasies. Juvenilizing terminal deletions were co mmon in the origin of homoplastic states but only slightly more so tha n novel substitutions and repatternings. Few homoplastic states arose via additions. Comparative studies on the origins of homoplasies are c urrently limited by the absence of developmental data for groups on wh ich cladistic analyses have been conducted, by multiple, equally parsi monious cladograms, and by the low number of homoplastic states that a re often available in clades.