Geographical phenotypic variation and reproductive system of a distylous Rubiaceae in the brazilian cerrado

• Ano de defesa: 2020
• Autor(a) principal: Doria, Maria Júlia Waldemarin
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Ecologia; Palicourea rigida; Polinização
• Link de acesso: http://hdl.handle.net/11449/202634

Palicourea rigida is a Rubiaceae species widely distributed across the Brazilian Cerrado. The species presents distyly, a type of floral dimorphism comprised of two floral morphs that are followed by a genetic heteromorphic self-incompatibility that enables the reproduction only after pollen flow between the distinct floral morphs. Palicourea rigida is typically pollinated by hummingbirds and has flowers varying in the color spectrum between orange and red. The species, however, presents a phenotypic variation across its distribution, and this variation includes floral size, color, and life form. In the southernmost distribution of the Cerrado vegetation, P. rigida presents a notoriously phenotypic variation with a markedly different life form, flower size, and color. In this sense, considering the phenotypic variation in Palicourea rigida populations either in life form and floral traits, as well as its dependence on pollinators for sexual reproduction, in this study we described the changes in the floral morphology of different populations of P. rigida and tested if they are followed by alterations of the basal features of distyly, i.e., breakdown of the heteromorphic self-incompatibility system, reciprocal hercogamy and isoplethy. Additionally, due to the change in flower color and size, we discussed the hypothesis of a potential pollinator shift from hummingbirds (ornithophily) to bees (melitophilly) in the dwarf population presenting yellow flowers as a possible outcome of pollinator-mediated selection. For this, we perform controlled pollination experiments in the southernmost dwarf population, analyzed the floral morphology, and evaluate floral color and pollinator perception. Our results showed that the basal features of distyly were maintained in the southernmost dwarf population, and the flowers are significantly smaller, with a larger stigmatic lobe in both floral morphs. Our results reinforce the role of inaccuracy in legitimate pollen deposition, where the higher inaccuracy in high organs seems to be responsible for lower pollen deposition at that level. Besides that, we found a pollinator shift from hummingbirds to bees in the population, even with no cognitive difference for bees when exposed to P. rigida yellow and reddish flowers.