Reproductive biology and pollinators in two enantiostylous Qualea species (Vochysiaceae) in the Brazilian Cerrado.

Enantiostyly is a floral polymorphism in which two floral forms in the same species differ in deflection of the stigma to right or left position. In monomorphic enantiostylous plants, flowers of the two morphs occur within the same individual, usually in the same proportion. In self-compatible species the function of monomorphic enantiostyly is proposed to increase outcrossing rates and offer a reproductive advantage under pollination limitation. Enantiostylous species are usually self-compatible and show heteranthery, with poricide anthers and pollen as pollinator reward; however, there are families, such as Vochysiaceae, that have different characteristics. We analysed the reproductive system and pollination biology of Qualea parviflora and Q. multiflora, two enantiostylous species from the Brazilian Cerrado that have specific morphological and physiological traits. For this, we characterized flower traits, performed hand pollinations and studied floral visitors. We found no differences between morphs in the proportion of flowers, nectar produced or its concentration, pollen quantity and fruit set. Both species were self-incompatible and quite generalist regarding floral visitors. Enantiostyly in self-incompatible plants seems to confer a reproductive advantage by reducing self-interference resulting from stigma clogging. This novel result helps to expand our knowledge on this complex floral polymorphism and opens new avenues for future research on this topic.

High species richness of native pollinators in Brazilian tomato crops / Alta riqueza de espécies de polinizadores nativos em plantações Brasileiras de tomateiro

Abstract Pollinators provide an essential service to natural ecosystems and agriculture. In tomatoes flowers, anthers are poricidal, pollen may drop from their pore when flowers are shaken by the wind. However, bees that vibrate these anthers increase pollen load on the stigma and in fruit production. The present study aimed to identify the pollinator richness of tomato flowers and investigate their morphological and functional traits related to the plant-pollinator interaction in plantations of Central Brazil. The time of anthesis, flower duration, and the number and viability of pollen grains and ovules were recorded. Floral visitors were observed and collected. Flower buds opened around 6h30 and closed around 18h00. They reopened on the following day at the same time in the morning, lasting on average 48 hours. The highest pollen availability occurred during the first hours of anthesis. Afterwards, the number of pollen grains declined, especially between 10h00 to 12h00, which is consistent with the pollinator visitation pattern. Forty bee species were found in the tomato fields, 30 of which were considered pollinators. We found that during the flowering period, plants offered an enormous amount of pollen to their visitors. These may explain the high richness and amount of bees that visit the tomato flowers in the study areas. The period of pollen availability and depletion throughout the day overlapped with the bees foraging period, suggesting that bees are highly effective in removing pollen grains from anthers. Many of these grains probably land on the stigma of the same flower, leading to self-pollination and subsequent fruit development. Native bees (Exomalopsis spp.) are effective pollinators of tomato flowers and are likely to contribute to increasing crop productivity. On the other hand, here tomato flowers offer large amounts of pollen resource to a high richness and amount of bees, showing a strong plant-pollinator interaction in the study agroecosystem.

Resumo Polinizadores fornecer um serviço essencial para os ecossistemas naturais e para agricultura. Em tomateiros, as anteras são poricidas e o pólen pode sair a partir dos poros quando as flores são agitadas pelo vento. No entanto, as abelhas que vibram as anteras aumentam a carga de pólen no estigma e na produção de frutos. O presente estudo teve como objetivo identificar a riqueza dos polinizadores das flores de tomate e investigar suas características morfológicas e funcionais relacionadas com a interação planta-polinizador em plantações do Brasil central. Foram registrados o tempo de antese, duração flor, bem como o número e viabilidade de grãos de pólen e óvulos. Os visitantes florais foram observados e coletados. Os botões florais abriram-se em torno 06h30 e fechou em torno de 18h00. As flores reabrem no dia seguinte ao mesmo tempo na parte da manhã, com longevidade média de 48 horas. A maior disponibilidade de pólen ocorreu durante as primeiras horas da antese. Depois disso, o número de grãos de pólen diminuiu, especialmente entre as 10h00 às 12h00, o que é consistente com os padrões de visitação de polinizadores. Quarenta espécies de abelhas foram encontradas nos campos de tomate, 30 das quais foram consideradas polinizadores. Durante o período de floração, as plantas oferecem enorme quantidade de pólen para os seus visitantes. Isto pode explicar a alta riqueza e quantidade de abelhas que visitam as flores de tomate nas áreas de estudo. O período de disponibilidade e redução de pólen durante todo o período do dia é sobreposto com o período de alimentação das abelhas, o que sugere que elas são altamente eficazes na remoção de grãos de pólen das anteras. Muitos desses grãos provavelmente são depositados no estigma da mesma flor, levando à auto-polinização e o desenvolvimento de frutos. Abelhas nativas (Exomalopsis spp.) são polinizadores efetivos de flores de tomate, podendo contribuir para o aumento da produtividade das culturas. Por outro lado, as flores de tomate oferecem grandes quantidades de pólen de recursos para uma alta riqueza e quantidade de abelhas, que mostram um estudo forte interação planta-polinizador nos agroecossistemas.

High species richness of native pollinators in Brazilian tomato crops.

Pollinators provide an essential service to natural ecosystems and agriculture. In tomatoes flowers, anthers are poricidal, pollen may drop from their pore when flowers are shaken by the wind. However, bees that vibrate these anthers increase pollen load on the stigma and in fruit production. The present study aimed to identify the pollinator richness of tomato flowers and investigate their morphological and functional traits related to the plant-pollinator interaction in plantations of Central Brazil. The time of anthesis, flower duration, and the number and viability of pollen grains and ovules were recorded. Floral visitors were observed and collected. Flower buds opened around 6h30 and closed around 18h00. They reopened on the following day at the same time in the morning, lasting on average 48 hours. The highest pollen availability occurred during the first hours of anthesis. Afterwards, the number of pollen grains declined, especially between 10h00 to 12h00, which is consistent with the pollinator visitation pattern. Forty bee species were found in the tomato fields, 30 of which were considered pollinators. We found that during the flowering period, plants offered an enormous amount of pollen to their visitors. These may explain the high richness and amount of bees that visit the tomato flowers in the study areas. The period of pollen availability and depletion throughout the day overlapped with the bees foraging period, suggesting that bees are highly effective in removing pollen grains from anthers. Many of these grains probably land on the stigma of the same flower, leading to self-pollination and subsequent fruit development. Native bees (Exomalopsis spp.) are effective pollinators of tomato flowers and are likely to contribute to increasing crop productivity. On the other hand, here tomato flowers offer large amounts of pollen resource to a high richness and amount of bees, showing a strong plant-pollinator interaction in the study agroecosystem.

Female Preference and Offspring Performance in the Seed Beetle Gibbobruchus bergamini Manfio & Ribeiro-Costa (Coleoptera: Chrysomelidae): A Multi-Scale Comparison.

The search for and choice of oviposition sites are a key step in the life cycle of herbivorous insects. Theory predicts that natural selection should favor the discrimination ability of female insects to select between high- and low-quality oviposition sites. However, correlation between female preference and offspring performance is apparently lacking or even negative in some herbivore-plant systems. A possible explanation for this seeming failure is that most studies have focused on a single factor and spatial scale. Here, we investigated the preference-performance relationship in the seed beetle Gibbobruchus bergamini Manfio & Ribeiro-Costa (Coleoptera: Chrysomelidae). We took into account several potential factors affecting oviposition choices and larval survivorship through a multi-level approach. Hierarchical analysis that controlled for the non-independence of observations demonstrated that oviposition site choices were not related to the factors that most influenced larval survivorship. The apparent effects of other pod-feeding herbivores were greater at the plant and branch scales while at the pod level the most important factors were plant-related variables. Oviposition choices seemed to be time-constrained, meaning that females have little opportunity to further increase offspring performance through additional compensatory choices.