<p>Determining the genetic basis of adaptation has become a central focus of evolutionary biology, and the incorporation of increasingly sophisticated analytical tools from molecular biology has made identifying causal genes a practical reality. The work presented herein addresses the effects of pleiotropic constraint on evolutionary change at the level of individual genes and genetic networks. In the first chapter, I combine molecular phylogenetic analyses and direct assays of enzymatic function to determine the evolutionary processes following a gene duplication in the anthocyanin pathway. My results show that, prior to duplication, the DFR gene was constrained from functional improvement by its multiple enzymatic roles. Following duplication, this constraint was released and adaptive evolution proceeded along both paralog lineages. In the second chapter, I determine the molecular genetic basis of a flower color transition that is associated with change in pollinator attraction in morning glories. A regulatory change in a branching gene in the flavonoid biosynthetic pathway restricted flux down the cyanidin-producing branch, conferring nearly exclusive production of red pelargonidin pigment in flowers. I further demonstrate that this regulatory change was restricted to floral tissue, and that ancestral pathway flux predominates in vegetative tissues. I propose that deleterious pleiotropic effects prevented evolutionary change via enzymatic changes in the pathway due to the numerous essential products downstream of this branching point. Together, these two results show that evolutionary change may be constrained by the molecular genetic context in which prospective adaptive mutations occur.</p> / Dissertation

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O estudo da ecologia floral à fundamental para o entendimento das relaÃÃes entre flores e seus visitantes, assim como para entender o papel dessa interaÃÃo no sucesso reprodutivo e na manutenÃÃo da populaÃÃo vegetal. No presente estudo, investigou-se a morfologia, a biologia floral e o sistema de reproduÃÃo de Ipomoea bahiensis Willd., bem como as interaÃÃes entre suas flores e a guilda de visitantes florais. A investigaÃÃo teve como objetivo central entender tanto as relaÃÃes ecolÃgicas e evolutivas entre I. bahiensis e insetos antÃfilos quanto o sistema reprodutivo da planta. Para tanto, foram empregados mÃtodos para analisar a morfologia funcional das flores, a relaÃÃo da morfologia e biologia floral com os visitantes, o comportamento e frequÃncia desses animais, o requerimento polÃnico e a relaÃÃo fruto/flor e, por fim, foi quantificada a limitaÃÃo de pÃlen. Para incrementar o conhecimento sobre a ecologia floral, foram observados os visitantes de nectÃrios extranupciais e sua relaÃÃo com inimigos florais. A partir da anÃlise dos dados obtidos, observou-se que as flores de I. bahiensis possuem atributos predominantemente de psicofilia, contudo tÃm plasticidade no sistemas de polinizaÃÃo, podendo ser polinizadas por abelhas de pequeno porte. A dinÃmica do nÃctar juntamente com o perÃodo de receptividade do estigma procura, possivelmente, garantir a visitaÃÃo de borboletas nesse perÃodo. No entanto, a variaÃÃo na frequÃncia dos visitantes florais foi entendida a partir da disponibilidade de pÃlen, pois os principais visitantes foram abelhas coletoras de pÃlen. Os testes de polinizaÃÃo mostraram que o sistema de reproduÃÃo à xenÃgamo, dependente de vetores biÃticos e apresenta auto-incompatibilidade. TambÃm foi observado que a planta à limitada por pÃlen / The study of floral ecology is pivotal to understanding the relationships between flowers and their visitors, as well as to understand the role of this interaction in reproductive success and maintenance of plant population. In this study, it was investigated the morphology, floral biology and breeding system of Ipomoea bahiensis Willd. and the interactions between its flowers and the guild of floral visitors. The research aimed mainly to understand the ecological and evolutionary relationships between I. bahiensis and anthophilous insects. For this, methods were used to analyze the functional morphology of flowers, the relationship of floral morphology and biology with visitors, the frequency and behavior these animals, the requirement for pollen and the rate fruit/flower and, finally, was estimated pollen limitation. To increase knowledge about the floral ecology were observed extranupcial nectariesâs visitors and its relation to floral enemies. From the analysis of the data, it was observed that the flowers of I. bahiensis have attributes predominantly psycophily, however they present plasticity in pollination systems, and can also be pollinated by small bees. The dynamics of nectar herewith with the period of stigma receptivity seeks to ensure the visitation of butterflies in this period. However, the variation in the frequency of floral visitors was understood from the availability of pollen, because the main visitors were bees pollen collecting. Pollination tests showed that the reproductive system is xenogamous, dependent on biotic vectors and presents self-incompatibility. It was also observed that the plant is limited by pollen

Specialization on insect and animal pollinators is thought to be the driving force for the evolution of floral traits. Specifically in the New World (NW), the oil-bee pollination syndrome has led to the convergence of floral characters in two distantly related families of core eudicots, Malpighiaceae and Krameriaceae. Both families display a flag-like structure that establishes a zygomorphic flower and floral oil rewards in epithelial elaiophores. These traits work concomitantly to attract and reward female oil-bees that help fertilize these flowers and in return receive oils. The underlying genetics of floral zygomorphy were studied in several clades of core eudicots, which implicated CYCLOIDEA2-(CYC2-)like genes of the TCP gene family to play a role in the establishment and maintenance of this trait. In Malpighiaceae, previous work demonstrated that two CYC2-like genes, CYC2A and CYC2B, are expressed during development correlated with establishing zygomorphy in flowers of NW Malpighiaceae. In this thesis work, I investigated the underlying developmental and genetic basis for the establishment of non-homologous and yet functionally similar traits in the oil-bee pollinated flowers of Malpighiaceae and Krameriaceae. In Chapter 1, I investigated the modification of a conserved CYC2 genetic program in the Old World (OW) acridocarpoids of Malpighiaceae following a major biogeographic disjunction. And in Chapter 2, I studied the floral ontogeny and genetic basis of floral zygomorphy development in Krameria lanceolata Torrey of Krameriaceae. This thesis work sheds light on the significance of the interdisciplinary study of floral symmetry evolution through comparative pollination ecology, development, and genetics.