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Master's Dissertation
DOI
https://doi.org/10.11606/D.59.2020.tde-17062021-190421
Document
Author
Full name
Danilo Ferreira Borges dos Santos
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Ribeirão Preto, 2020
Supervisor
Committee
Claro, Kleber Del (President)
Guimaraes Junior, Paulo Roberto
Pereira, Rodrigo Augusto Santinelo
Silva, Diego Vinícius Anjos
Title in Portuguese
Formigas visitantes de nectários pericarpiais de Rubiaceae: impactos de uma relação mutualística
Keywords in Portuguese
Mutualismo de proteção
Nectário pericarpial
Rubiaceae
Abstract in Portuguese
O mutualismo é uma interação de exploração mútua na qual as espécies interagentes se beneficiam. Um exemplo é o mutualismo de proteção formado entre formigas e plantas portadoras de nectários extraflorais. Nesse caso, as formigas defendem a planta ao forragearem em busca do néctar, diminuindo danos foliares e florais, e consequentemente aumentando o fitness da planta. Algumas espécies de plantas apresentam nectários florais que após a queda da corola continuam a produzir néctar sobre o fruto em desenvolvimento, denominado nectário pericarpial (NP). Embora comum nos Neotrópicos, poucos estudos tem dado atenção para a interação entre formigas e NPs. O principal objetivo deste estudo foi avaliar na savana brasileira, a comunidade e o comportamento das formigas associadas a plantas portadoras de NPs; e descrever a estrutura da rede formiga-planta. A hipótese levantada foi que essa rede terá uma estrutura aninhada, e que as principais formigas associadas serão a de comportamento agressivo em plantas com maior concentração e volume de néctar pericarpial, como as formigas Camponotus crassus e Ectatomma tuberculatum. O estudo de campo foi conduzido em uma área de cerrado durante o período de frutificação das espécies. As espécies de plantas utilizadas pertencem a família Rubiaceae: Cordiera elliptica, Declieuxia fruticosa e Palicourea rigida. Foram feitas observações em campo para avaliar a rede ecológica, e diferentes manipulações experimentais foram realizadas para a avaliação da agressividade das formigas e taxa de herbivoria foliar. O néctar pericarpial foi mensurado em volume e concentração de açúcar assim como sua relação com a abundância de formigas nas plantas. Os resultados mostraram que os NPs podem mediar a interação entre formigas e plantas no cerrado, influenciando na estrutura da rede, bem como no comportamento e na diversidade de formigas associadas. As redes apresentaram uma estrutura aninhada para duas espécies de plantas. E como esperado, as formigas C. crassus e E. tuberculatum estiveram presentes nas três espécies de plantas e apresentaram altos valores de grau e força de interação. As formigas associadas a essas plantas oferecem uma defesa efetiva contra a herbivoria foliar em Cordiera elliptica e Palicourea rigida, mas não em Declieuxia fruticosa. A abundância e agressividade das formigas são influenciadas de acordo com a concentração do néctar pericarpial oferecido pelas plantas. E por fim, tanto as características das formigas, como dominância e agressividade quanto as características das plantas como concentração do néctar, são fatores que contribuem para estruturação da rede.
Title in English
Visiting ants of Rubiaceae pericarpial nectaries: impacts of a mutualistic relationship
Keywords in English
Mutualism of protection
Pericarpial nectary
Rubiaceae
Abstract in English
Mutualism is an interaction of mutual exploitation in which interacting species benefit. An example is the protective mutualism formed between ants and plants that carry extrafloral nectaries. In this case, the ants defend the plant by foraging in search of nectar, reducing leaf and flower damage, and consequently increasing the plant's fitness. Some plant species have floral nectaries that, after the fall of the corolla, continue to produce nectar on the developing fruit, called pericarpial nectary (NP). Although common in the Neotropics, few studies have given attention to the interaction between ants and NPs. The main objective of this study was to evaluate in the Brazilian savannah, the community and the behaviour of ants associated with plants carrying NPs; and describe the structure of the ant-plant network. The hypothesis raised was that this network will have a nested structure, and that the main associated ants will be aggressive in plants with higher concentration and volume of pericarpial nectar, such as the ants Camponotus crassus and Ectatomma tuberculatum. The field study was conducted in an area of Cerrado during the period of fruiting of the species. The plant species used belong to the Rubiaceae family: Cordiera elliptica, Declieuxia fruticosa and Palicourea rigida. Field observations were made to assess the ecological network, and different experimental manipulations were carried out to assess the ant's aggressiveness and leaf herbivory rate. The pericarpial nectar was measured in volume and concentration of sugar as well as its relationship with the abundance of ants in the plants. The results showed that NPs can mediate the interaction between ants and plants in the Cerrado, influencing the structure of the network, as well as the behaviour and diversity of associated ants. The nets presented a nested structure for two species of plants. And as expected, the ants C. crassus and E. tuberculatum were present in the three species of plants and showed high values of degree and strength of interaction. The ants associated with these plants offer an effective defence against leaf herbivory in Cordiera elliptica and Palicourea rigida, but not in Declieuxia fruticosa. Ants' abundance and aggressiveness are influenced according to the concentration of pericarpial nectar offered by plants. And finally, both the characteristics of ants, such as dominance and aggressiveness as well as the characteristics of plants such as concentration of nectar, are factors that contribute to the structuring of the network.
 
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Publishing Date
2021-06-21
 
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