Phylogeny and ecology of dioecious fig pollination

The evolution of mutualistic interactions between the dioecious figs (Ficus subg. Ficus, Moraceae) and their pollinating wasps (Hymenoptera: Agaonidae) was examined using comparative methods. Fig species are either monoecious or gynodioecious depending on the arrangement of unisexual florets within the specialized inflorescence or syconium. Due to complex interactions with pollinators (Agaoninae), the gynodioecious species are functionally dioecious. In Chapter 1, the evolutionary relationships of dioecious figs were examined through phylogenetic analyses based on the internal transcribed spacer region of nuclear ribosomal DNA (nrDNA) and morphology. Chapter 2 describes a parallel study of the pollinators of dioecious figs using mitochondrial DNA (mtDNA) sequences and morphology. Separate and combined analyses suggest that neither dioecious figs nor their pollinators are monophyletic. However, fig/pollinator associations were largely congruent with phylogy and support a revised classification of Ficus.; Comparative analyses in Chapter 3 examined aspects of coevolution including the cospeciation of interacting lineages and the coadaptation of interacting traits. Parallel phylogenies and correlated rates of evolution in fig nrDNA and pollinator mtDNA sequences support a history of cospeciation. Reconstructions of breeding system evolution indicated that dioecy evolved once or twice with at least two reversals to monoecy in a dioecious lineage. Changes in pollinator ovipositor length were correlated with changes in fig breeding system. The correlated evolution of fig style lengths and pollinator ovipositors, suggests a role for coadaptation in the regulation of resource conflicts between mutualists.; Chapter 4 summarizes ecological studies in New Guinea, examining the impact of non- pollinating fig wasps on the mutualism and suggesting a new hypothesis for the origin and maintenance of dioecious fig pollination. Chapter 5 presents an argument that fig pollination is an extreme case of coevolution in plant/insect interactions. The associations of herbivores in a range of insect guilds were poorly correlated with host phylogeny, compared to the associations of specialized fig wasps. Most Ficus herbivores in New Guinea, including leaf chewing and sap sucking insects, are oligophagous and their patterns of association are not explained by host phylogeny, suggesting that other factors play an important role in shaping interactions between plants and insects in general.