DO BIOCHEMICAL EXAPTATIONS LINK EVOLUTION OF PLANT DEFENSE AND POLLINATION SYSTEMS - HISTORICAL HYPOTHESES AND EXPERIMENTAL TESTS WITH DALECHAMPIA VINES

Mapping resin secretion and pollination ecology onto the estimated phy logeny of species of the euphorb vine Dalechampia generated two histor ical hypotheses: resin rewards offered to pollinators by Dalechampia f lowers evolved by minor modification of a preexisting, resin-based, fl oral defense system, and resin defense of leaves in advanced species e volved by modification of the preexisting resin-reward system. From th ese hypotheses, we derived two predictions: floral reward resins are c hemically similar to putative floral defense resins and exhibit antihe rbivore activities, and foliar resins are chemically similar to reward resins and also exhibit antiherbivore activities. We tested these pre dictions by chemical analyses and by using a broad sample of Neotropic al herbivorous insects in a series of bioassays. All floral and foliar resins were chemically similar. Tests with two generalist (Orophus te sselatus, Orthoptera: Tettigoniidae; Atta colombica, Hymenoptera: Form icidae) and four Dalechampia-specialist herbivores (Syphraea sp., Cole optera: Chrysomelidae; Ectima rectifasciata, Hamadryas ipthime, and Ha madryas amphinome, Lepidoptera: Nymphalidae) showed floral and foliar resin to deter significantly feeding or leaf cutting. These results su pport our two hypotheses and indicate that, in this system, biochemica l exaptations have played a major role in the evolution of plant-insec t relationships, adaptations reducing herbivory have affected the evol ution of plant-pollinator relationships, and adaptations for pollinati on have affected the evolution of plant-herbivore relationships.