J. Javier G. Quezada-Euán

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.

THE AFRICANIZATION OF HONEYBEES (APIS MELLIFERA L.) OF THE YUCATAN:A STUDY OF A MASSIVE HYBRIDIZATION EVENT ACROSS TIME

Abstract Until recently, African and European subspecies of the honeybee (Apis mellifera L.) had been geographically separated for around 10,000 years. However, human‐assisted introductions have caused the mixing of large populations of African and European subspecies in South and Central America, permitting an unprecedented opportunity to study a large‐scale hybridization event using molecular analyses. We obtained reference populations from Europe, Africa, and South America and used these to provide baseline information for a microsatellite and mitochondrial analysis of the process of Africanization of the bees of the Yucatan Peninsula, Mexico. The genetic structure of the Yucatecan population has changed dramatically over time. The pre‐Africanized Yucatecan population (1985) comprised bees that were most similar to samples from southeastern Europe and northern and western Europe. Three years after the arrival of Africanized bees (1989), substantial paternal gene flow had occurred from feral Africanized drones into the resident European population, but maternal gene flow from the invading Africanized population into the local population was negligible. However by 1998, there was a radical shift with both African nuclear alleles (65%) and African‐derived mitochondria (61%) dominating the genomes of domestic colonies. We suggest that although European mitochondria may eventually be driven to extinction in the feral population, stable introgression of European nuclear alleles has occurred.

The effect of food reserves on the production of sexual offspring in the stingless bee Melipona beecheii (Apidae, Meliponini)

Summary. A long-term study on the production of sexual offspring in relation to food stores was conducted in the stingless bee Melipona beecheii. Firstly, the production of sexuals was followed during one year in 10 colonies kept under natural conditions. Of the brood produced, 22.9% were males, and of all female brood, 14.6% were queens. Secondly, we measured the effect of experimentally manipulating the amount of food stores. One set of colonies started with 1.5 kg of food reserves and were regularly fed with pollen and nectar while another set were subjected to reduced food reserves of 0.5 kg, and were not given any extra food. Throughout the study, colonies with no treatment had brood and adults of both sexes all year round with no evidence of their presence being linked to swarming. Colonies with reduced food stores produced fewer males (0.7%) and queens (10.5%) than untreated colonies or colonies with enlarged food stores. The production of sexuals in colonies with enlarged food stores (23.4% males, 13.5% queens) did not differ significantly from that under natural conditions.¶We conclude that in Melipona only colonies that have accumulated large food stores produce sexuals that contribute to the reproductive population. This may lead to marked differences in the amount of sexuals produced by different colonies, although at the population level sexuals may be present all year round.

Not Only Single Mating in Stingless Bees

Abstract. Queens of the large, pantropical and fully eusocial taxon Meliponinae (stingless bees) are generally considered to be singly mated. We indirectly estimated queen mating frequency in two meliponids, Melipona beecheii and Scaptotrigona postica, by examining genotypes of workers at microsatellite DNA loci. Microsatellites were highly variable, providing suitable markers with which to assign patrilinial origin of workers within colonies headed by single queens. Queen mating frequency varied between 1 and 3 (M. beecheii) and 1 and 6 (S. postica), representing the first clear documentation of polyandry in the Meliponinae. Effective paternity frequency, me, was lower, although above 2 for S. postica. Stingless bees may provide suitable subjects for the testing of recent inclusive fitness arguments describing intracolony kin conflict in social Hymenoptera.

An olfactory shift is associated with male perfume differentiation and species divergence in orchid bees.

Saltational changes may underlie the diversification of pheromone communication systems in insects, which are normally under stabilizing selection favoring high specificity in signals and signal perception. In orchid bees (Euglossini), the production of male signals depends on the sense of smell: males collect complex blends of volatiles (perfumes) from their environment, which are later emitted as pheromone analogs at mating sites. We analyzed the behavioral and antennal response to perfume components in two male morphotypes of Euglossa cf. viridissima from Mexico, which differ in the number of mandibular teeth. Tridentate males collected 2-hydroxy-6-nona-1,3-dienyl-benzaldehyde (HNDB) as the dominant component of their perfume. In bidentate males, blends were broadly similar but lacked HNDB. Population genetic analysis revealed that tri- and bidentate males belong to two reproductively isolated lineages. Electroantennogram tests (EAG and GC-EAD) showed substantially lower antennal responses to HNDB in bidentate versus tridentate males, revealing for the first time a mechanism by which closely related species acquire different chemical compounds from their habitat. The component-specific differences in perfume perception and collection in males of two sibling species are in agreement with a saltational, olfaction-driven mode of signal perfume evolution. However, the response of females to the diverged signals remains unknown.

Enfleurage, lipid recycling and the origin of perfume collection in orchid bees

Enfleurage, the extraction of elusive floral scents with the help of a lipophilic carrier (grease), is widely used in the perfume industry. Male neotropical orchid bees (Euglossini), which accumulate exogenous fragrances as pheromone analogues, use a similar technique. To collect fragrances, the bees apply large amounts of straight-chain lipids to odoriferous surfaces from their cephalic labial glands, which dissolve the volatiles, and the mixture is then transferred to voluminous hind-leg pockets. Here, we show that males do in fact operate a lipid conveyor belt to accumulate and concentrate their perfume. From the hind-leg pockets of caged male Euglossa viridissima, deuterated derivatives of carrier lipids were consecutively sequestered, shuttled back to the labial glands and reused on consecutive bouts of fragrance collection. Such lipid cycling is instrumental in creating complex perfume bouquets. Furthermore, we found that labial glands of male orchid bees are strikingly similar to those of scent-marking male bumblebees in terms of size, form and structure. This, and a prominent overlap in secretory products, led us to propose that perfume collection evolved from scent-marking in ancestral corbiculate bees.

Morphometric and genetic differentiation in isolated populations of the endangered Mesoamerican stingless bee Melipona yucatanica (Hymenoptera: Apoidea) suggest the existence of a two species complex

The stingless bee Melipona yucatanica is a rare species only found in preserved forests across Mesoamerica. Morphometric and molecular analyses (DNA barcoding of the cytochrome oxidase (cox1) and microsatellites) were combined to characterize and compare populations from Mexico and Guatemala. We aim to test the hypothesis predicting that populations from these two geographic regions could be considered as distinct taxonomic units. Morphometric analyses revealed geographic differences, Guatemalan bees being larger than Mexican specimens. Bayesian analyses of the mitochondrial cox1 region and the microsatellite loci demonstrated that M. yucatanica form two clades corresponding to the Mexican and Guatemalan populations. These results suggest that M. yucatanica from Mexico and Guatemala could represent two distinct species. However, more studies are needed on their ecology and behavior to determine the possibility of gene flow between them.

Beekeeping in the Yucatan peninsula: development and current status

This article reviews the development and present state of beekeeping in the Yucatan peninsula. It describes the particular situation of small-scale peasant beekeepers who collectively produce a substantial quantity of honey which is sold at competitive prices on the international market. A short historical overview gives the evolution from honey production with stingless bees to a modern beekeeping industry with the honey bee, Apis mellifera. The current beekeeping situation is described, including the status of honey production, its commercialization and exportation. Finally, the main problems that beekeepers face are summarized and future prospects for apiculture in the region suggested.

Conservation genetics of neotropical pollinators revisited: microsatellite analysis suggests that diploid males are rare in orchid bees.

Allozyme analyses have suggested that Neotropical orchid bee (Euglossini) pollinators are vulnerable because of putative high frequencies of diploid males, a result of loss of sex allele diversity in small hymenopteran populations with single locus complementary sex determination. Our analysis of 1010 males from 27 species of euglossine bees sampled across the Neotropics at 2–11 polymorphic microsatellite loci revealed only five diploid males at an overall frequency of 0.005 (95% CIs 0.002–0.010); errors through genetic nondetection of diploid males were likely small. In contrast to allozyme‐based studies, we detected very weak or insignificant population genetic structure, even for a pair of populations >500 km apart, possibly accounting for low diploid male frequencies. Technical flaws in previous allozyme‐based analyses have probably led to considerable overestimation of diploid male production in orchid bees. Other factors may have a more immediate impact on population persistence than the genetic load imposed by diploid males on these important Neotropical pollinators.

Rapid evolution of chemosensory receptor genes in a pair of sibling species of orchid bees (Apidae: Euglossini)

BackgroundInsects rely more on chemical signals (semiochemicals) than on any other sensory modality to find, identify, and choose mates. In most insects, pheromone production is typically regulated through biosynthetic pathways, whereas pheromone sensory detection is controlled by the olfactory system. Orchid bees are exceptional in that their semiochemicals are not produced metabolically, but instead male bees collect odoriferous compounds (perfumes) from the environment and store them in specialized hind-leg pockets to subsequently expose during courtship display. Thus, the olfactory sensory system of orchid bees simultaneously controls male perfume traits (sender components) and female preferences (receiver components). This functional linkage increases the opportunities for parallel evolution of male traits and female preferences, particularly in response to genetic changes of chemosensory detection (e.g. Odorant Receptor genes). To identify whether shifts in pheromone composition among related lineages of orchid bees are associated with divergence in chemosensory genes of the olfactory periphery, we searched for patterns of divergent selection across the antennal transcriptomes of two recently diverged sibling species Euglossa dilemma and E. viridissima.ResultsWe identified 3185 orthologous genes including 94 chemosensory loci from five different gene families (Odorant Receptors, Ionotropic Receptors, Gustatory Receptors, Odorant Binding Proteins, and Chemosensory Proteins). Our results revealed that orthologs with signatures of divergent selection between E. dilemma and E. viridissima were significantly enriched for chemosensory genes. Notably, elevated signals of divergent selection were almost exclusively observed among chemosensory receptors (i.e. Odorant Receptors).ConclusionsOur results suggest that rapid changes in the chemosensory gene family occurred among closely related species of orchid bees. These findings are consistent with the hypothesis that strong divergent selection acting on chemosensory receptor genes plays an important role in the evolution and diversification of insect pheromone systems.