Camila Maia-Silva

The recruiter's excitement--features of thoracic vibrations during the honey bee's waggle dance related to food source profitability.

SUMMARY The honey bees waggle dance constitutes a remarkable example of an efficient code allowing social exploitation of available feeding sites. In addition to indicating the position (distance, direction) of a food patch, both the occurrence and frequency of the dances depend on the profitability of the exploited resource (sugar concentration, solution flow rate). During the waggle dance, successful foragers generate pulsed thoracic vibrations that putatively serve as a source of different kinds of information for hive bees, who cannot visually decode dances in the darkness of the hive. In the present study, we asked whether these vibrations are a reliable estimator of the excitement of the dancer when food profitability changes in terms of both sugar concentration and solution flow rate. The probability of producing thoracic vibrations as well as several features related to their intensity during the waggle phase (pulse duration, velocity amplitude, duty cycle) increased with both these profitability variables. The number of vibratory pulses, however, was independent of sugar concentration and reward rate exploited. Thus, pulse number could indeed be used by dance followers as reliable information about food source distance, as suggested in previous studies. The variability of the dancers thoracic vibrations in relation to changes in food profitability suggests their role as an indicator of the recruiters motivational state. Hence, the vibrations could make an important contribution to forager reactivation and, consequently, to the organisation of collective foraging processes in honey bees.

Survival strategies of stingless bees (Melipona subnitida) in an unpredictable environment, the Brazilian tropical dry forest

Unpredictable environments are a challenge to highly eusocial bees because unreliable food availability, owing mainly to seasonally unpredictable precipitation rates, renders the maintenance of permanent colonies difficult. Here, we investigated the strategy of the stingless bee Melipona subnitida to cope with elevated temperatures and extended, irregular periods of drought in the Brazilian tropical dry forest. We found a high association between colony behaviour (pollen foraging and brood production) and environmental parameters (abiotic factors and availability of pollen sources), suggesting that colonies tightly adjust their activities to the respective environmental conditions. This minimises unnecessary costs related to foraging and brood rearing when forage availability is low. Additionally, M. subnitida selectively foraged at the most lucrative pollen-sources (mass-flowering trees, plants with poricidal flowers), which indicates that the colonies maximise their food intake as soon as resources are available.

On the Diversity of Foraging-Related Traits in Stingless Bees

Stingless bee pot-honey is a valuable product with a long tradition of harvest and consumption. The differences found among meliponine honeys with respect to their physicochemical composition, sugar content, and floral origin depend not only on the geographic region but also on the stingless bee species kept for honey production. Tropical habitats are frequently shared by several dozen meliponine species and, consequently, diet overlap in terms of food plants used is considerable. Competition and the selective pressure to maximise food collection shaped a rich variety of foraging-related traits among the stingless bees. In the present chapter, we want to give a brief overview of this diversity, discussing the importance of morphological traits (tongue length, body colour, and body size) for the separation of fundamental food niches among the Meliponini. In contrast to a species’ fundamental niche, which is delimited by the morphological and physiological characteristics of an organism, the food niche realised by a species is determined through the interactions with other organisms that share the same fundamental food niche. Here, differences in foraging strategy among the stingless bees with regard to aggression, recruitment ability, and recruitment precision influence dominance relationships at a feeding site and, thus, are important factors concerning the partitioning of resources.

On the thermal limits for the use of stingless bees as pollinators in commercial greenhouses

Stingless bees (Apidae, Meliponini) are frequently used as crop pollinators in tropical countries. The present study calls attention to the thermal limit for the use of these bees as pollinators in commercial greenhouses, in which the temperature frequently exceeds that of the outside environment. We assessed the thermal biology of Melipona subnitida, a stingless bee species that naturally occurs in north-eastern Brazil, a region characterized by elevated ambient temperatures all year round. The critical (CTN) and lethal limits (LTN) for worker bees under long-term temperature exposure (24 h) were 40 and 44 °C respectively when individuals had access to water, or 39 and 42 °C respectively without water. Due to limited active colony thermoregulation of this species, the temperatures inside the nests were similar to the ambient temperature. In their natural environment, nest temperatures never exceeded CTN. In strong contrast, inside a greenhouse, the nest temperatures exceeded the critical value nearly every day due to the high ambient temperatures in this closed environment. As a result, the colonies weakened critically and had to be removed from the greenhouse after 14 days. Our study emphasizes the need for both thermo-physiological investigations and management strategies when planning the use of bees as pollinators for greenhouse crops, particularly so in tropical regions, where temperatures in these enclosed environments may easily exceed the thermal limits of a species.

Nectar profitability, not empty honey stores, stimulate recruitment and foraging in Melipona scutellaris (Apidae, Meliponini)

In stingless bees (Meliponini) like in many other eusocial insect colonies food hoarding plays an important role in colony survival. However, very little is known on how Meliponini, a taxon restricted to tropical and subtropical regions, respond to different store conditions. We studied the impact of honey removal on nectar foraging activity and recruitment behaviour in Melipona scutellaris and compared our results with studies of the honey bee Apis mellifera. As expected, foraging activity increased significantly during abundance of artificial nectar and when increasing its profitability. Foraging activity on colony level could thereby frequently increase by an order of magnitude. Intriguingly, however, poor honey store conditions did not induce increased nectar foraging or recruitment activity. We discuss possible reasons explaining why increasing recruitment and foraging activity are not used by meliponines to compensate for poor food conditions in the nest. Among these are meliponine specific adaptations to climatic and environmental conditions, as well as physiology and brood rearing, such as mass provisioning of the brood.

Protecting a managed bee pollinator against climate change: strategies for an area with extreme climatic conditions and socioeconomic vulnerability

In the semiarid region of Northeastern Brazil, populations of native bees can be jeopardized by future climate change. The present study aims to analyze the impact of climate change on a native stingless bee (Melipona subnitida Ducke). This species is a locally important pollinator of wild and crop plants, also exploited for honey production by regional beekeepers. Using species distributional modeling, we assessed the effects of climate change on the geographic distribution of M. subnitida. We found a potential shift in future areas where species can find climatically suitable habitats toward the edges of the current pollinator distribution with a consequent central disconnection, which can threaten species dispersal and gene flow. We propose to reconnect the remaining suitable areas through conservation and restoration programs based on the distribution of the plant species that are used by this bee as source of pollen and nectar and propose also, other strategies that aim to increase the welfare of local people

The Contribution of Palynological Surveys to Stingless Bee Conservation: A Case Study with Melipona subnitida

Melipona subnitida (Apidae, Meliponini) is one of the few social bee species naturally occurring in the Brazilian tropical dry forest, where the vast majority of food plants are available during a short and unpredictable rainy season. It is a key species concerning the pollination of native plants as well as agricultural crops and has great potential for commercial honey production. However, severe habitat loss over the past century has caused a considerable decline of native bee populations, which demands effective conservation/restoration strategies to protect these important pollinators. In the present chapter, we discuss how melittopalynological studies may help to establish such conservation plans. In the first part, we outline the floral origin of pollen and nectar harvested by colonies of the stingless bee M. subnitida in the dry forest. The second part discusses the importance of knowledge on floral preferences and flowering schedules as solid bases for management plans that may contribute toward reconstruction of suitable habitats for this bee species.