Interações entre Protodiscelis (Colletidae, Neopasiphaeinae) e plantas aquáticas e a importância de odores florais na atração de polinizadores.
| Ano de defesa: | 2012 |
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| Autor(a) principal: | |
| Orientador(a): | |
| Banca de defesa: | |
| Tipo de documento: | Tese |
| Tipo de acesso: | Acesso aberto |
| Idioma: | por |
| Instituição de defesa: |
Universidade Federal da Paraíba
Brasil Zoologia Programa de Pós-Graduação em Ciências Biológicas UFPB |
| Programa de Pós-Graduação: |
Não Informado pela instituição
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| Departamento: |
Não Informado pela instituição
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| País: |
Não Informado pela instituição
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| Palavras-chave em Português: | |
| Link de acesso: | https://repositorio.ufpb.br/jspui/handle/tede/4107 |
Resumo: | Bees are the main pollinators in terrestrial environments. Plants are sessile organisms that only attain cross-sexual reproduction through the activity of pollen vectors. As such, flowers offer hints for the interspecific encounter; they obtain pollination services and in exchange, usually, they provide floral resources to pollinators. The main resource sought by bees is pollen, which is used as larval nourishment. From the plants standpoint, however, there must be a balance between the offered resource and the amount of pollen grains effectively transferred to the stigmas. Such balance is dictated by a number of variables; pollinator attractivity, pollinator effectiveness, quantity of pollen exported/received and the energy allotted in the reproductive process. Aware of this paradox and observing that flowers exhibit specific traits associated with certain groups of pollinators (floral syndromes), there has been a tendency among researchers to evaluate flower evolution as if it were directed towards specialization. Nonetheless, specialization is associated to the referential group and behaves within a continuum of plain generalization and high specialization. I have studied two groups of bees: one a specialist and the other a generalist, although adapted to a rare niche among bees the nocturnal habit. I studied specialized bees of the genus Protodiscelis (Colletidae, Neopasiphaeinae), a group that exhibits feeding habit specialization, and their interaction with flowers. Protodiscelis bees are oligolectic, meaning that they are genetically determined to collect pollen grains for larval provisioning among phylogenetically constraint plant taxa. These bees will only gather pollen from species of the family Alismataceae, a group comprised of aquatic herbs common to lentic ecosystems. I investigated the pollination of four species belonging to this family and aimed to understand the plant-pollinator interactions within a spatial and morphofunctional frame, which also involves the floral cues used by the bees in order to find they preferred host flowers. I divided the obtained results into three upcoming publications, each dealing with one of the analyzed themes. The pollination of Echinodorus palaefolius was studied in several flooded areas in the Caatinga. Additionally I investigated the relationships between bees and flowers of five other species of the same genus (E. subalatus, E. glandulosus, E. paniculatus, E. pubescens e Echinodorus sp.). Echinodorus palaefolius is self-incompatible and relied on pollinators to develop fruits. The phenology of the species is dictated by the rain regime and flowers were visited by three bee species alone: Protodiscelis alismatis, Apis mellifera and Trigona spinipes. Surprisingly, the morphologically generalist flowers of this plant species are visited by an oligolectic bee (P. alismatis) and by the two among the most generalist of bees (A. mellifera and T. spinipes). The oligolectic species, however, was accounted with over 80% of flower visits. Bees of P. alismatis exhibit clear behavioral and morphological adaptations, such as extremely plumose setae that can hold the small pollen grains of Echinodorus. They were present in 96% of the 41 flooded areas that I sampled in the Caatinga. Bees of P. alismatis were also the main pollinators of the other species of Echinodorus collected within over 1,000 km of natural distribution of the Caatinga. The specialized relationship of these bees with their host plants is highly consistent in the insular environments of the Caatinga, where the aquatic Alismataceae naturally occur. The pollination ecology of three species of a neotropical clade limnocharitaceae (Alismataceae) was studied among distinct populations in northeast Brazil and middle-west Brazil. The results of pollination ecology were compared to those of H. martii, previously studied. I researched the morphological attributes and the aspects of the reproductive system that differentiate these species. Limnocharis flava, L. laforestii and Hydrocleys nymphoides were all visited by Protodiscelis palpalis, the same oligolectic species previously recognized as the sole effective pollinator of H. martii. Flowers of L. flava were found to be morphologically and functionally similar to those of H. martii. In both species, the presence of staminodes protect the pollen and bees of P. palpalis alone were effective pollinators, due to an adapted behavior that allows them to access the pollen chamber. The flowers of L. laforestii, on the other hand, were effectively pollinated by other species of bees, regardless of the presence of staminodes. But in this case, no protective pollen chamber is formed. In the population of the municipality of Serra Negra do Norte, P. palpalis was replaced by a yet undescribed species of Protodiscelis. For Limnocharis, however, animal pollen vectors are not required for fruit development and both studied species yielded high seed counts through autogamy. The flowers of H. nymphoides are larger and bear staminodes that do promote filtering of other bee species. Regardless of genetic self-incompatibility, H. nymphoides is pollinated by several generalist bee species, notably the social T. spinipes, A. mellifera and Bombus brevivilus (Apidae). Knowing that autogamy is one of the main variables for the establishment and dissemination of plants in biological invasions (Baker s Law), the occurrence of this type of pollination may largely explain the invasive status of the three studied species in Asia, Oceania and North America. The generalist association with pollinators would explain the invasions observed for H. nymphoides. I used the sampling method of dynamic headspace and gas chromatography coupled to mass spectrometry (GC-MS) to describe the volatile compounds emitted by the flowers of H. martii and H. nymphoides. I tested the attractivity of the main isolated compounds to bees of Protodiscelis palpalis in field conditions. Floral scents in the family Alismataceae were described for the first time. Flowers of H. martii produced a bouquet comprised of 22 compounds, whereas the bouquet of H. nymphoides contained 13 compounds. Each species, despite sharing several compounds, present a characteristic floral scent profile. Methoxylated benzenoids were the main constituents of the bouquets of H. martii and H. nymphoides. ρ-Methylanisole is the main compound in the floral scent of H. martii and 3,4-dimethoxytoluene the main compound in H. nymphoides. These two compounds, however, were isolated in both species. ρ-methylanisole, 2-methoxy-4-methylphenol, 3,4-dimethoxytoluene, 3,4,5-trimethoxytoluene and methyl salicylate were used in field biotests with artificial flowers assembled from yellow and blue adhesive paper. Only ρ-methylanisole yielded significantly more approaches from bees towards artificial flowers of both colors in comparison to control flowers. Artificial yellow flowers, however, proportionally attracted more bees than blue flowers. Ours results, the first ever obtained in a natural environment setting, show that a single volatile compound attracts female P. palpalis and is the most important communication channel between these pollinators and flowers of H. martii e H. nymphoides. Our results reinforce the fact that specific volatile compounds present in flower bouquets might be crucial for the localization of host plants by oligoletic bees. Bees of Megalopta (Halictidae, Augochlorini) are nocturnal and explore a niche that is mostly inaccessible to other bees. In the interaction between Megalopta bees and their host plants I studied one of the signals emitted by the flowers: floral scents. Scents have long been known as pollinator attractants, but little is known about the identity of the compounds produced by flowers and which among them incite behavioral responses of animals, such as pollinator attraction. I selected volatile compounds commonly isolated in floral scents and conducted field attraction biotests with Megalopta bees. I tackled the hypotheses that such common floral scent compounds, frequently identified in night-blooming angiosperms, would be involved in the attraction of Megalopta bees. I found out that single aromatic compounds effectively attracted female bees and elicited visiting behavior. Bees were significantly more attracted to traps baited with benzyl acetate, benzyl benzoate and methyl salicylate than to unbaited traps or traps baited with compounds less frequently isolated in night-blooming flowers (β-ionone, eucalyptol, eugenol and vanillin). I concluded that Megalopta bees use scents to find flowers under low-light conditions, as observed by several other groups of nocturnal pollinators. Moreover, I provided a new sampling technique for these rarely collected insects. |