The Roles of Ontogenetic Evolution in the Origins of Floral Homoplasies

Homoplasy, manifest as convergence, parallelism, or reversal, is an important aspect of floral diversity. Few studies have focused on the evolution of floral homoplasies, and the role of ontogenetic evolution in their origins has been largely ignored. Four clades of angiosperms, the genera Besseya (Scrophulariaceae) and Eucnide (Loasaceae), the family Hydrangeaceae, and the order Piperales, were used to examine the roles of ontogenetic evolution in creating floral homoplasies. The possible modes of ontogenetic evolution were found to contribute unequally to the origin of homoplasies. Juvenilizing terminal deletions were common in the origin of homoplastic states but only slightly more so than novel substitutions and repatternings. Few homoplastic states arose via additions. Comparative studies on the origins of homoplasies are currently limited by the absence of developmental data for groups on which cladistic analyses have been conducted, by multiple, equally parsimonious cladograms, and by the low number of homoplastic states that are often available in clades.