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dc.contributor.advisorMartinez del Rio, Carlosen_US
dc.contributor.advisorBronstein, Judith L.en_US
dc.contributor.authorSchondube-Friedewold, Jorge
dc.creatorSchondube-Friedewold, Jorgeen_US
dc.date.accessioned2013-04-11T08:59:53Z
dc.date.available2013-04-11T08:59:53Z
dc.date.issued2003en_US
dc.identifier.urihttp://hdl.handle.net/10150/280325
dc.description.abstractNectarivory has evolved independently eight times among birds. In the neotropics specialized nectarivory evolved in hummingbirds and flowerpiercers (genus Diglossa). Flowerpiercers are nectar-robbers of hummingbird-pollinated plants. Because flowerpiercers and hummingbirds are found in the same habitats feeding on the nectar of the same flowers, they provide us with a unique opportunity to understand the pressures that nectarivory imposes on animals. Flowerpiercers present beaks that have a long hook at the tip of their maxilla. The hook is used to hold tubular flowers in place while they stab them by projecting their lower mandible. Then, they insert their tongues in the puncture and extract nectar. I investigated the following questions: (1) What is the function of the flowerpiercer's hook, and which are the consequences of its evolution? (2) Are the digestive traits of flowerpiercers convergent with those of hummingbirds? (3) How do digestive traits affect sugar selection by nectar feeding birds? And (4) What are the effects of Diglossa baritula's physiology and behavior over its annual cycles? I found that nectarivorous flowerpiercers evolved from a frugivorous ancestor with a hookless beak. The evolution of a hooked bill allowed flowerpiercers to become efficient nectar-robers, but hindered their efficiency to feed on fruit. Using a phylogenetically informed approach, I found that the digestive traits of flowerpiercers and hummingbirds are not convergent. Unlike hummingbirds which have astounding intestinal sucrase activity levels, flowerpiercers had low sucrase activity. Nectar intake in D. baritula seems to be limited by its ability to digest sucrose. I also found that sugar preferences in nectar-feeding birds are concentration-dependent. At lower concentrations birds preferred hexoses, whereas at higher concentrations they preferred sucrose. Although nectar composition and concentration are often discussed as two different floral traits, they have a synergistic effect on the sugar preferences of nectar-feeding birds. D. baritula individuals exhibit biannual reproductive and molting cycles that are synchronized with flower and fruit abundance in the mountains of Mexico. The ability to rob nectar appears to have molded the evolution of the most important morphological, physiological and behavioral traits of D. baritula.
dc.language.isoen_USen_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.subjectBiology, Ecology.en_US
dc.subjectBiology, Animal Physiology.en_US
dc.subjectBiology, Zoology.en_US
dc.titleFlowerpiercers and hummingbirds: A comparative study of nectar feeding strategies in birdsen_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
thesis.degree.grantorUniversity of Arizonaen_US
thesis.degree.leveldoctoralen_US
dc.identifier.proquest3090016en_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineEcology & Evolutionary Biologyen_US
thesis.degree.namePh.D.en_US
dc.identifier.bibrecord.b4442596xen_US
refterms.dateFOA2018-05-26T04:37:32Z
html.description.abstractNectarivory has evolved independently eight times among birds. In the neotropics specialized nectarivory evolved in hummingbirds and flowerpiercers (genus Diglossa). Flowerpiercers are nectar-robbers of hummingbird-pollinated plants. Because flowerpiercers and hummingbirds are found in the same habitats feeding on the nectar of the same flowers, they provide us with a unique opportunity to understand the pressures that nectarivory imposes on animals. Flowerpiercers present beaks that have a long hook at the tip of their maxilla. The hook is used to hold tubular flowers in place while they stab them by projecting their lower mandible. Then, they insert their tongues in the puncture and extract nectar. I investigated the following questions: (1) What is the function of the flowerpiercer's hook, and which are the consequences of its evolution? (2) Are the digestive traits of flowerpiercers convergent with those of hummingbirds? (3) How do digestive traits affect sugar selection by nectar feeding birds? And (4) What are the effects of Diglossa baritula's physiology and behavior over its annual cycles? I found that nectarivorous flowerpiercers evolved from a frugivorous ancestor with a hookless beak. The evolution of a hooked bill allowed flowerpiercers to become efficient nectar-robers, but hindered their efficiency to feed on fruit. Using a phylogenetically informed approach, I found that the digestive traits of flowerpiercers and hummingbirds are not convergent. Unlike hummingbirds which have astounding intestinal sucrase activity levels, flowerpiercers had low sucrase activity. Nectar intake in D. baritula seems to be limited by its ability to digest sucrose. I also found that sugar preferences in nectar-feeding birds are concentration-dependent. At lower concentrations birds preferred hexoses, whereas at higher concentrations they preferred sucrose. Although nectar composition and concentration are often discussed as two different floral traits, they have a synergistic effect on the sugar preferences of nectar-feeding birds. D. baritula individuals exhibit biannual reproductive and molting cycles that are synchronized with flower and fruit abundance in the mountains of Mexico. The ability to rob nectar appears to have molded the evolution of the most important morphological, physiological and behavioral traits of D. baritula.


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