XVI International Botanical Congess

Comparative analyses of the pantropical vine Dalechampia, based on nuclear ribosomal (ITS-1, 5.8S, ITS-2) and chloroplast (trnK intron) DNA phylogenies, show similar floral trait/function relationships among most neotropical and paleotropical species. Malagasy species, however, are highly incongruent with other species due to rapid, divergent evolution. Synthesis of cladistic and ecological data indicate that: 1) Malagasy species descended relatively recently from African ancestors and experienced high rates of divergence in floral ecology. 2) Novel selective pressures generated by a different pollinator fauna in Madagascar caused a sudden reversal from specialized pollination based on a terpene-resin reward to generalized pollination based on a pollen reward. 3) Subsequent to this reversal, specialization again increased in one Malagasy clade, with buzz-pollination evolving through neoteny.