Astrid de Matos Peixoto Kleinert

Diversity, threats and conservation of native bees in the Neotropics

The Neotropics bee fauna is very rich with 5000 recognised species, including 33 genera (391 species) of Meliponini, but it is estimated to be at least three fold greater in species richness. Deforestation, agriculture intensification and introduction/spread of exotic competing bee species are considered the main threats to most indigenous species, although other less obvious causes can affect the populations of some bee species locally. Efforts to conserve the native bee fauna include better knowledge of bee richness and diversity (standardized surveys, larger bee collections and appropriate identification of bee species) and of their population dynamics, raising of public and policy makers’ awareness, commercial applications of bee products and services such as pollination and preservation of natural habitat.ZusammenfassungDie vorliegende Arbeit soll einen Überblick geben über die Diversität und den Artenreichtum der neotropischen Bienenfauna, die Bedrohungen, denen sie ausgesetzt ist, als auch eine Darstellung der Initiativen und Probleme im Artenschutz der einheimischen Bienen. Die Daten beruhen auf umfassenden Literaturrecherchen. Diese Informationen wurden dann von den Autoren diskutiert und in Form relevanter Punkte inhaltlich zusammengefasst. Das Ergebnis zeigt, dass die Neotropis eine artenreiche Bienenfauna aufweist und dass diese sogar unterschätzt wird. Den existierenden 5000 gültigen Artennamen stehen Schätzungen gegenüber, dass diese weniger als ein Drittel der tatsächlich vorkommenden Arten umfassen (Tab. I). Bedrohungen, denen einheimische Bienen der Neotropis ausgesetzt sind, liegen vor allem menschliche Aktivitäten zugrunde, die in drei Kategorien zusammengefasst werden können: Entwaldung, Intensivierung der Landwirtschaft und Einführung fremder Arten. Die Hauptursachen der Entwaldung sind Holzeinschlag, das Sammeln von Feuerholz, die Produktion von Holzkohle und Rodungen zur Schaffung von landwirtschaftlichen und Weideflächen. Der Amazonasregenwald, Mexiko und Zentralamerika weisen die höchsten Entwaldungsraten in Amerika auf, aber auch in den Chaco-Wälder der argentinischen und kolumbianischen Anden schreitet die Entwaldung fort (Tab. II). Die Ausbreitung und Intensivierung der Landwirtschaft wird vielfach als die wichtigste Bedrohung für Bienenarten angesehen. Sie führt zu einer Verringerung der Artendiversität bei Tieren und Pflanzen, verringert das Angebot an Nistmöglichkeiten und Futterquellen, und durch das Ausbringen von Pestiziden und Pflügen der Böden werden sowohl Bienenlarven als auch Adulte getötet. Ironischerweise sind die meisten Kulturpflanzen mehr oder weniger stark auf die Präsenz biotischer Bestäuber angewiesen, wobei die Bienen die wichtigste Gruppe darstellen. Auch die Einführung fremder Bienenarten und anderer exotischer Organismen, die mit der lokalen Bienenfauna in Wechselwirkung treten, kann die einheimische Bienenfauna beeinträchtigen. Die Einführung von Apis mellifera in die Neue Welt zur Steigerung der Honigproduktion und die von exotischen Hummelarten für Bestäubungszwecke hat zu Bedenken Anlass gegeben über die Konkurrenz mit einheimischen Bienen um Futter- und Nistmöglichkeiten, sowie zur Ausbreitung von Krankheiten und Parasiten und zur Hybridisierung mit einheimischen Hummmelarten. Anderen Bedrohungen liegen Trockenzeiten, Überschwemmungen, grossflächige Buschbrände, Hurrikane und die Kontaminierung der Ökosysteme mit Schwermetallen zugrunde. Die Hauptprobleme, denen sich Initiativen zum Artenschutz einheimischer Bienen gegenübersehen, sind fehlende Kenntnisse über Artenreichtum, Diversität, Taxonomie, Populationsdynamik und den Einfluss menschlicher Aktivitäten auf die meisten Bienenarten. Um zu besseren Kenntnissen über Artenreichtum, Diversität und Populationsdynamik zu kommen, ist Öffentlichkeitsarbeit und Aufklärung bei Politikverantwortlichen erforderlich. Hierin können die Kommerzialisierung von Bienenprodukten, sowie Aufklärung über die Bedeutung von Bestäubern und der Schutz natürlicher Habitate eine wichtige Rolle spielen. Bestäuberinitiativen erweisen sich hierbei als wichtige Werkzeuge, um Politiker, die Öffenlichkeit und Forscher in koordinierter Weise zusammenzubringen, Wissen über wichtige Fragen zu schaffen und insbesondere die negativen Auswirkungen bienenbedrohender Aktivitäten in Lateinamerika abzumildern.

Identification of oxygen containing volatiles in cephalic secretions of workers of Brazilian stingless bees

Os constituintes volateis das secrecoes cefalicas de 11 especies brasileiras de abelhas sem ferrao da linha Tetragonisca - Tetragona foram analisados. Foram identificados 145 compostos, por cromatografia gasosa e espectrometria de massas, dentre os quais 72 esteres, 22 alcoois, 16 acidos carboxilicos, 13 terpenos, 8 aldeidos, 4 compostos aromaticos, 2 lactonas e 1 diidropirano. As relacoes estruturais, origem e a distribuicao detes compostos sao discutidas. Com respeito a composicao qualitativa e quantitativa, cada especie mostra um buque de odores, os quais sao obtidos a partir de componentes poucos especificos. Em algumas especies proximamente relacionadas foram observadas similaridades no buque de odores. As fragmentacoes no espectro de massas de esteres graxos e dos esteres insaturados derivatizados com DMDS sao discutidas em detalhes.

Connectance of Brazilian social bee: food plant networks is influenced by habitat, but not by latitude, altitude or network size

Several recent studies suggest that the level of generalization (measured as percentage connectance) of plantpollinator networks has several ecological correlates, e.g. latitude and altitude. Here we report on levels of generalization in 27 two-mode networks of social bees and their food plants in various Brazilian habitats and urban environments. Social bees are generalist foragers and are among the most abundant flower visitors in Brazil. They probably account for 30-50% of all plant – flower visitor interactions. Connectance was significantly influenced by habitat. Cerrado forests showed lower connectance than the dry dune habitats, with Atlantic rain forest and urban sites taking intermediate position and arid Caatinga being similar to dunes. This shows that generalization in a plant – flower visitor community can be influenced by habitat even within a group of generalist flower visitors, in our case social bees. We show that the strength of the interactions is not different between Cerrado and semi-arid habitats (dunes and Caatinga) and discuss other explanations for our findings.

Could Tetragonisca angustula latreille (Apinae, Meliponini) be effective as strawberry pollinator in greenhouses?

We evaluated the contribution of the stingless bee Tetragonisca angustula as a strawberry pollinator using primary flowers of the ‘Oso Grande’ cultivar. We applied 4 pollination treatments: open-pollination in the field, T. angustula pollination inside a greenhouse, and spontaneous self-pollination in the field and greenhouse. In each treatment we determined berry weight, number of achenes, number of fertilised ovules, fertilisation rates, and the percentage of marketable fruit. The results showed that one colony of this species in a greenhouse with approximately 1350 strawberry plants was adequate to pollinate ‘Oso Grande’ primary flowers. The contribution of T. angustula to the weight and shape of primary berries demonstrated that this bee species is an effective strawberry pollinator and it can promote a significant increase in overall strawberry production.

Foraging behavior of Melipona rufiventris Lepeletier (Apinae; Meliponini) in Ubatuba, SP, Brazil

This study describes how the foraging activity of Melipona rufiventris is influenced by the environment and/or by the state of a colony. Two colonies were studied in Ubatuba, SP (44 degrees 48 W and 23 degrees 22 S) from July/2000 to June/2001. These colonies were classified as strong (Colony 1) and intermediate (Colony 2) according to their general conditions: population and brood comb size and number of food pots. The bees were active from dawn to dusk. The number of pollen loads presented a positive correlation with relative humidity (r(s) = 0.401; p <0.01) and was highest between 70 and 90%. However, it was negatively correlated with temperature (r(s) = -0.228; p <0.01) showing a peak between 18 and 23 degrees C. The number of nectar loads presented a positive correlation with temperature (r(s) = 0.244; p <0.01) and light intensity (r(s) = 0.414; p <0.01); it was greater between 50 and 90% of relative humidity and 20 and 30 degrees C of temperature. They collected more nectar than pollen throughout the day, and were more active between 6 and 9 hours. Workers from Colony 1 (strong) collected nectar in greater amounts and earlier than those from Colony 2 (intermediate). The number of pollen, nectar and resin loads varied considerably between the study days. Peaks of pollen collection occurred earlier in months with longer days and in a hotter and more humid climate. The foraging behavior of M. rufiventris is probably affected by the state of the colony and by environmental conditions, notably temperature, relative humidity, light intensity and length of the day.

Abundance and Flower Visits of Bees in a Cerrado of Bahia, Tropical Brazil

AbstractAbundance, seasonal phenology and flower visits of eusocial bees were studied in Diamantina, a national park with cerrado vegetation in Bahia, tropical Brazil. About 700 bees were collected, mainly native stingless bees and the introduced Africanized honey bee. Sampling along a transect was most effective March through September during the dry season. The foraging worker bees were observed on flowers of over 60 angiosperm species of which a few were visited with high frequency. Foraging activity concentrated on flowering plants of the families Leguminosae and Asteraceae. The results are discussed under aspects of nutritional resource partitioning by bee communities in neotropical habitats and the specific composition of a cerrado apifauna.

Structure of bee-flower system in the coastal sand dune of Abaeté, northeastern Brazil

For twelve months (from January to December of 1996) we investigated bee-flower interactions in a sea coastal ecosystem in Bahia, Brazil. Samples were taken three times each month. 3983 individuals belonging to 49 bee species, grouped in 13 morph-functional categories, visited 66 plant species belonging to 39 botanic families. It was observed 310 interactions between bees and plants at species level. The use of floral resources by bees was not homogeneous; most of the plant species received a low number of visitors. No restricted plant-bee species relationship in resource use concerning the subset of analyzed interactions was detected. In Abaete the generalist relationships predominated.

Monogamy in large bee societies: a stingless paradox

High genetic diversity is important for the functioning of large insect societies. Across the social Hymenoptera (ants, bees, and wasps), species with the largest colonies tend to have a high colony-level genetic diversity resulting from multiple queens (polygyny) or queens that mate with multiple males (polyandry). Here we studied the genetic structure of Trigona spinipes, a stingless bee species with colonies an order of magnitude larger than those of polyandrous honeybees. Genotypes of adult workers and pupae from 43 nests distributed across three Brazilian biomes showed that T. spinipes colonies are usually headed by one singly mated queen. Apart from revealing a notable exception from the general incidence of high genetic diversity in large insect societies, our results reinforce previous findings suggesting the absence of polyandry in stingless bees and provide evidence against the sperm limitation hypothesis for the evolution of polyandry. Stingless bee species with large colonies, such as T. spinipes, thus seem promising study models to unravel alternative mechanisms to increase genetic diversity within colonies or understand the adaptive value of low genetic diversity in large insect societies.

A community of flower-visiting bees (Hymenoptera: Apoidea) in the coastal sand dunes of northeastern Brazil

We analyzed aspects of the community structure of Apoidea of a restricted area of dunes with restinga vegetation in Salvador, Bahia, Brazil. Standardized samples were taken for one year, 3 times a month from 6:00 a.m. to 6:00 p.m. A total of 3983 individuals (3770 females and 213 males) of 49 species, grouped into 13 morpho-functional types and belonging to five families, were collected from flowers in its majority. The fauna of Abaete is composed by large solitary bees, best represented by Anthophoridae followed by Apidae; Halictidae; Megachilidae and Colletidae. Bees were active throughout the year, with peaks of abundance in periods of low rainfall. Daily activity was greatest between 08:00 and 14:00 hours, when relative humidity was lower and temperature higher. The abundance pattern and the richness were very similar to other habitats in the Brazilian Northeast. Of the species sampled, 49% were represented by less than eight individuals. The six most abundant species were represented by 84% of the total individuals collected. The availability of resources seems to be the main factor regulating bee flight activity in Abaete. The foraging activity was related positively to the intensity of flowers in the field.

Native and Non-Native Supergeneralist Bee Species Have Different Effects on Plant-Bee Networks

Supergeneralists, defined as species that interact with multiple groups of species in ecological networks, can act as important connectors of otherwise disconnected species subsets. In Brazil, there are two supergeneralist bees: the honeybee Apis mellifera, a non-native species, and Trigona spinipes, a native stingless bee. We compared the role of both species and the effect of geographic and local factors on networks by addressing three questions: 1) Do both species have similar abundance and interaction patterns (degree and strength) in plant-bee networks? 2) Are both species equally influential to the network structure (nestedness, connectance, and plant and bee niche overlap)? 3) How are these species affected by geographic (altitude, temperature, precipitation) and local (natural vs. disturbed habitat) factors? We analyzed 21 plant-bee weighted interaction networks, encompassing most of the main biomes in Brazil. We found no significant difference between both species in abundance, in the number of plant species with which each bee species interacts (degree), and in the sum of their dependencies (strength). Structural equation models revealed the effect of A. mellifera and T. spinipes, respectively, on the interaction network pattern (nestedness) and in the similarity in bee’s interactive partners (bee niche overlap). It is most likely that the recent invasion of A. mellifera resulted in its rapid settlement inside the core of species that retain the largest number of interactions, resulting in a strong influence on nestedness. However, the long-term interaction between native T. spinipes and other bees most likely has a more direct effect on their interactive behavior. Moreover, temperature negatively affected A. mellifera bees, whereas disturbed habitats positively affected T. spinipes. Conversely, precipitation showed no effect. Being positively (T. spinipes) or indifferently (A. mellifera) affected by disturbed habitats makes these species prone to pollinate plant species in these areas, which are potentially poor in pollinators.