RESUMO
Abstract The present study describes the behavior of male Emphorini bees in exploiting Convolvulaceae flowers as sleeping-sheltering place. The observations occurred inadvertently during a field study in an Agroforestry System in the Caatinga region, near the banks of the São Francisco River in Petrolina, Pernambuco - NE-Brazil. Males were observed and collected in wilted flowers of Ipomoea carnea (Convolvulaceae) during the evening. The sampling revealed nine Emphorini bees, belonging to three oligolectic species specialized on Convolvulaceae. We propose that the infundibuliform morphology of Ipomoea carnea flowers and the varied timing of anthesis could influence the choice of these flowers as overnight resting places. Furthermore, we endorse the idea present in the literature that males of oligolectic bees generally engage in patrolling flowers utilized by females, thereby enhancing the chances of encountering potential mates, making these flowers rendezvous places. The observation of this behavior highlights the interdependence between bees and plants and raises the possibility that the loss of these flowers could negatively impact bees not only in a nutrition aspect but also regarding shelter and reproduction.
Resumo O presente estudo documenta o comportamento de abelhas machos do grupo Emphorini em explorar flores da família Convolvulaceae como local para dormir e se abrigar. As observações foram realizadas inadvertidamente durante um estudo de campo em um Sistema Agroflorestal na região da Caatinga, próximo às margens do Rio São Francisco, em Petrolina, Pernambuco - Nordeste do Brasil. Machos foram observados e coletados em flores fechadas de Ipomoea carnea (Convolvulaceae) durante o entardecer. Em nossa amostragem, encontramos nove machos da tribo Emphorini, pertencentes a três espécies oligoléticas especializadas em Convolvulaceae. Propomos que a morfologia infundibuliforme das flores de Ipomoea carnea e os diferentes períodos de antese das flores podem influenciar a escolha dessas flores como locais de descanso durante à noite. Além disso, nossos dados endossam a ideia de que machos de abelhas oligoléticas geralmente patrulham flores utilizadas por fêmeas, aumentando assim as chances de encontrar possíveis parceiras, tornando essas flores locais de encontro para acasalamento. O registro desse comportamento destaca a interdependência entre abelhas e plantas e levanta a possibilidade de que a perda dessas flores possa impactar negativamente as abelhas não apenas em relação a sua nutrição, mas também em relação ao abrigo e reprodução.
RESUMO
Analyses of resource presentation, floral morphology and pollinator behaviour are essential for understanding specialised plant-pollinator systems. We investigated whether foraging by individual bee pollinators fits the floral morphology and functioning of Blumenbachia insignis, whose flowers are characterised by a nectar scale-staminode complex and pollen release by thigmonastic stamen movements. We described pollen and nectar presentation, analysed the breeding system and the foraging strategy of bee pollinators. We determined the nectar production pattern and documented variations in the longevity of floral phases and stigmatic pollen loads of pollinator-visited and unvisited flowers. Bicolletes indigoticus (Colletidae) was the sole pollinator with females revisiting flowers in staminate and pistillate phases at short intervals, guaranteeing cross-pollen flow. Nectar stored in the nectar scale-staminode complex had a high sugar concentration and was produced continuously in minute amounts (~0.09 µl·h-1 ). Pushing the scales outward, bees took up nectar, triggering stamen movements and accelerating pollen presentation. Experimental simulation of this nectar uptake increased the number of moved stamens per hour by a factor of four. Flowers visited by pollinators received six-fold more pollen on the stigma than unvisited flowers, had shortened staminate and pistillate phases and increased fruit and seed set. Flower handling and foraging by Bicolletes indigoticus were consonant with the complex flower morphology and functioning of Blumenbachia insignis. Continuous nectar production in minute quantities but at high sugar concentration influences the pollen foraging of the bees. Partitioning of resources lead to absolute flower fidelity and stereotyped foraging behaviour by the sole effective oligolectic bee pollinator.
Assuntos
Abelhas , Magnoliopsida , Polinização , Animais , Abelhas/fisiologia , Feminino , Flores , Magnoliopsida/fisiologia , Néctar de Plantas , Polinização/fisiologiaRESUMO
Opuntia (Cactaceae) is known for high rates of hybridization and ploidisation, resulting in the formation of new species. The occurrence of two sympatric and closely related species of Opuntia, O. elata and O. retrorsa, in Brazilian Chaco enabled us to test the hypothesis that pre-zygotic reproductive isolation mechanisms operate in both species. We monitored the flowering period, as well as floral biology, and compared the morphological variation of floral structures through measurements, performed intra- and interspecific cross-pollination tests, and recorded the guild of floral visitors and pollinators. Flowering was seasonal and highly synchronous. Floral biology exhibits similar strategies, and although floral morphology differs significantly in many of the compared structures, such morphological variation does not result in the selection of exclusive pollinators. Floral visitors and pollinators are oligolectic bees shared by both species. Opuntia elata and O. retrorsa are self-compatible. While interspecific cross-pollination (bidirectional) resulted in germination, the pollen tube did not penetrate the stigma. Opuntia elata and O. retrorsa are closely related; however, they are isolated and do not hybridise in Brazilian Chaco. We found that both have weak pre-pollination barriers, but that they are strongly isolated by pollen-pistil incompatibility, i.e. post-pollination barrier.