Quantitative conservation genetics of wild and managed bees

Quantitative genetic traits provide insights into the evolutionary potential of populations, as heritability estimates measure the population’s ability to respond to global changes. Although wild and managed bees are increasingly threatened by the degradation of natural habitats and climate change, risking plant biodiversity and agriculture production, no study has yet performed a systematic review of heritability estimates across the group. Here we help fill this knowledge gap, gathering all available heritability estimates for ants, bees, and wasps, evaluating which factors affect these estimates and assessing the reported genetic correlations between traits. Using a model selection approach to analyze a dataset of more than 800 heritability estimates, we found that heritability is influenced by trait type, with morphological traits exhibiting the highest heritability estimates, and defense and metabolism-related traits showing the lowest estimates. Study system, sociality degree, experimental design, estimation type (narrow or broad-sense heritability), and sample size were not found to affect heritability estimates. Results remained unaltered when correcting for phylogenetic inertia, and when analyzing social bees separately. Genetic correlations between honeybee traits revealed both positive coefficients, usually for traits in the same category, and negative coefficients, suggesting trade-offs among other traits. We discuss these findings and highlight the importance of maintaining genetic variance in fitness-related traits. Our study shows the importance of considering heritability estimates and genetic correlations when designing breeding and conservation programs. We hope this meta-analysis helps identify sustainable breeding approaches and conservation strategies that help safeguard the evolutionary potential of wild and managed bees.     

Mortality rates of honey bees in the wild

Senescence, defined as an age-specific decrease in physiological performance accompanied by an increase in mortality rate, has been studied in a wide range of animals including social insects. It is not clear, however, whether honey bees in the wild live long enough to exhibit senescent decline. I tested for the effects of senescence on honey bees foraging in natural settings and documented the predicted pattern of exponential increase in mortality rate with forager age. These data indicate that, in spite of high rates of external mortality, senescence is an important factor determining the performance of insects such as honey bees in the wild. Received 16 November 2007; revised 1 February 2008 and 10 March 2008; accepted 18 March 2008.     

Additional Techniques for Studying the behavior of wild bees

Summary This supplement to a paper byLinsley et al. (1952) describes techniques for the study of socialHalictidæ as well as other bees. Methods used to judge relative ages of bees include study of mandibular wear and wing wear. Marking of individuals with quick drying paints is described. Marked bees may be returned to their nest through a glass tube. Paints often wear off; more permanent marking may be achieved by staining wings with an alcohol or acetone solution of methyl or ethyl eosin. Methods are described for delaying bees as they enter or leave their nest, so that color markings can be more easily seen. Small wire screen cones placed over nest entrances often serve this purpose. Methods of obtaining data from nests which are very close together are described, as well as methods of making population estimates of bees by means of the Lincoln Index. The following observations on each bee are recommended to learn as much as possible of habits and caste differences: (1) size of ovaries, (2) number of enlarged ovarioles, (3) number and size of largest oocytes, (4) presence of sperm cells in spermatheca, (5) presence of pollen in gut, (6) length of wing or some other index of size, (7) amount of wing and mandibular wear. The pollen loads of bees entering a nest can be marked with powder of different colors. Subsequent examination of cell provisions shows how many foragers cooperated in provisioning a cell. Replacement of a part of a nest with a glass tube provides opportunities for study of activities inside of the nest.

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Zusammenfassung Die vorliegende Arbeit, ein Nachtrag zu dem Artikel vonLinsley et al. (1952), beschreibt Methoden für das Studium der sozialenHalicitidæ und anderer Bienen. Das relative Alter der Bienen kann durch Bewertung der Abnützung von Mandibeln und Flügeln geschätzt werden. Einzelne Bienen können durch schnell trocknende Farben gekennzeichnet werden. Derart markierte Individuen werden mittels einer Glaßröhre züruck in das Nest gebracht. Dauerhafter als Farben oder Lacke, welche sich oft abreiben, sind Markierungen mit Alkohol- oder Azetonlösungen von Methyl- oder Ethyl-Eosin an den Flügeln. Methoden zum Aufhalten von Bienen beim Verlassen des Nestes oder bei der Rückkehr sind hier beschrieben. Eine dieser Methoden, die der näheren Untersuchung von Farbmarkierungen dienen, ist das Stellen von Drahtnetztüten über den Nesteingang. Erwähnt werden auch Methoden zur Beobachtung von nah-beieinanderliegenden Nestern. Die Bevölkerungszahl kann mit Hilfe des Lincoln Indexes geschätzt werden. Wir empfehlen die folgenden Untersuchungen an jeder Biene um soviel als möglich über das Verhalten und die Kastenunterschiede zu lernen: (1) Größe der Eierstöcke, (2) Anzahl der vergrößerten Ovariolen, (3) Anzahl und Größe der größten Oocyten, (4) Vorhandensein von Spermien in der Samenblase, (5) Vorhandensein von Blütenstaub im Darm, (6) Flügellänge oder ein anderes Maß der allgemeinen Größe, (7) Grad der Flügel- und Mandibelabnützung. Die Blütenstaublasten von Bienen können vor dem Betreten des Nestes mit Farbpulvern bestaubt werden. Darauf folgende Untersuchung der Verpflegungsmassen der einzelnen Zellen ergibt die Anzahl der Futtersammler, die eine einzelne Zelle mit Proviant versorgt haben. Der Ersatz eines Teils des Nestes durch eine Glaßröhre gibt Gelegenheit zum Studium des Verhaltens innerhalb des Nestes.

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Résumé Dans ce complément à une note deLinsley et ses collaborateurs, les auteurs décrivent des techniques qui peuvent être utilisées dans l'étude desHalictidæ sociaux ou d'autres Abeilles.Les méthodes employées pour apprécier les âges relatifs des Abeilles comportent, entre autres, l'étude de l'usure mandibulaire et de l'usure alaire. On décrit le marquage des individus avec des peintures à séchage rapide. Les Abeilles marquées peuvent être replacées dans le nid à l'aide d'un tube en verre. Les peintures s'usent souvent; on peut obtenir un marquage plus tenace en colorant les ailes avec une solution de méthyl ou d'éthyl éosine dans l'alcool ou l'acétone. On décrit des techniques permettant de diminuer la densité relative des Abeilles qui entrent dans le nid ou qui travaillent à l'intérieur, de façon à rendre les marques colorées plus facilement visibles. De petits écrans coniques en cire placés devant l'entrée du nid peuvent remplir cet office. On décrit des méthodes permettant d'obtenir des résultats sur des nids complètement clos et des méthodes d'estimation de populations par l'emploi de l'indice de Lincoln. De manière à recueillir le plus d'indications possible sur les habitudes des différentes castes, on préconise les observations suivantes: 1^o taille des ovaires; 2^o nombre d'ovarioles dilatés; 3^o nombre et taille des plus grands ovocytes; 4^o présence de spermatozoïdes dans la spermathèque; 5^o présence de pollen dans le jabot; 6^o longueur des ailes ou quelque autre indice de taille; 7^o degré de l'usure mandibulaire ou alaire.Les pelotes polliniques des Abeilles entrant dans le nid peuvent être marquées au moyen de poudres de différentes couleurs. L'examen ultérieur des provisions contenues dans les cellules indique combien de butineuses coopèrent à l'approvisionnement d'une seule cellule. La substitution d'une paroi de verre à la paroi du nid permet l'étude directe des activités des Abeilles dans le nid.

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Contribution number 890 from the Department of Entomology, University of Kansas, Lawrence, Kansas, U. S. A. This study was conducted with the aid of a grant from the National Science Foundation.     

The mycoflora of domesticated and wild bees (Apoidea)

Fungi including yeasts are common in the honey stomachs and provisions of diverse bees. They may be parasites, commensals or mutualistic. Yeasts, singly or in association with bacteria, are pioneer colonizers during a microbial succession in larval cells of many subterranean bees. They are followed by fungi such asAspergillus, Penicillium, Emericellopsis, Sartorya, Pseudoarachniotus, Gymnoascus, Carpenteles andFusarium. Aspergillus flavus andSaccharomyces spp. are pathogenic to many species of bees, and fungi are the main cause of declining alkali bee populations. There are 124 species of fungi, including 36 new records, associated with Apoidea; 49 species are associated with alkali bees.Cooperative investigations of the Plant Sciences Research (L. R. Batra) and Entomology (G. E. Bohart) Divisions, Agricultural Research Service, U.S. Department of Agriculture, and the Utah Agricultural Experiment Station, Logan, Utah.     

Dispersal capacity and diet breadth modify the response of wild bees to habitat loss

Habitat loss poses a major threat to biodiversity, and species-specific extinction risks are inextricably linked to life-history characteristics. This relationship is still poorly documented for many functionally important taxa, and at larger continental scales. With data from five replicated field studies from three countries, we examined how species richness of wild bees varies with habitat patch size. We hypothesized that the form of this relationship is affected by body size, degree of host plant specialization and sociality. Across all species, we found a positive species–area slope (z = 0.19), and species traits modified this relationship. Large-bodied generalists had a lower z value than small generalists. Contrary to predictions, small specialists had similar or slightly lower z value compared with large specialists, and small generalists also tended to be more strongly affected by habitat loss as compared with small specialists. Social bees were negatively affected by habitat loss (z = 0.11) irrespective of body size. We conclude that habitat loss leads to clear shifts in the species composition of wild bee communities.     

Management increases genetic diversity of honey bees via admixture

The process of domestication often brings about profound changes in levels of genetic variation in animals and plants. The honey bee, Apis mellifera, has been managed by humans for centuries for both honey and wax production and crop pollination. Human management and selective breeding are believed to have caused reductions in genetic diversity in honey bee populations, thereby contributing to the global declines threatening this ecologically and economically important insect. However, previous studies supporting this claim mostly relied on population genetic comparisons of European and African (or Africanized) honey bee races; such conclusions require reassessment given recent evidence demonstrating that the honey bee originated in Africa and colonized Europe via two independent expansions. We sampled honey bee workers from two managed populations in North America and Europe as well as several old-world progenitor populations in Africa, East and West Europe. Managed bees had highly introgressed genomes representing admixture between East and West European progenitor populations. We found that managed honey bees actually have higher levels of genetic diversity compared with their progenitors in East and West Europe, providing an unusual example whereby human management increases genetic diversity by promoting admixture. The relationship between genetic diversity and honey bee declines is tenuous given that managed bees have more genetic diversity than their progenitors and many viable domesticated animals.     

Beta diversity of orchid bees in a tropical biodiversity hotspot

A controversial issue in ecology and conservation is whether community composition is controlled by niche or dispersal assembly. We assessed the importance of climatic factors and geographic gradients on the distribution of orchid bees in a severely-fragmented and species-rich tropical forest region in Brazil. Orchid-bee males were attracted to 17 different scent baits and collected in 15 forest sites. In total we captured 11,081 bees from 40 species. Climatic variables explained twice as much of the observed variation in the bee species data set as did pure spatial variation. However, most of the climatic explained variation was spatially structured, indicating that the species and the climatic data have a similar spatial arrangement. In fact, part of the observed latitudinal changes in community composition appears to be explained by a concomitant gradient in precipitation seasonality. Similarly, reduced temperatures and a more seasonal precipitation may help to explain the relative distinctiveness of the fauna from some of the westernmost sites. The level of similarity among the sampled sites, although highly variable, decayed both as function of the climatic and geographic distances among these sites. The greatest pairwise dissimilarities in the composition of the orchid-bee fauna were observed among sites 200–300 km from each other, since in many case those sites were more dissimilar in terms of climate than those further apart. It is suggested that global warming and consequent altered climatic regimes will influence the distribution patterns of orchid bees in a region already threatened by deforestation and forest fragmentation.     

Response of microbial communities of Lake Baikal to extreme temperatures

The survival rate, metabolic activity, and ability for growth of microbial communities of Lake Baikal have been first studied after exposure to extremely low temperatures (freeze-thawing) for different lengths of time. It has been shown that short-term freezing (1–3 days) inhibits the growth and activity of microbial communities. The quantity of microorganisms increased after 7-and 15-day freezing. In the periods of maximums, the total number of microorganisms in the test samples was twice as high as in the control. It was established that after more prolonged freezing the microorganisms required more time after thawing to adapt to new conditions. In the variants with 7-and 15-day freezing, the activities of defrosted microbial communities were three or more times higher than in the control. The survival rate and activity of Baikal microorganisms after freeze-thawing confirms the fact that the Baikal microbial communities are highly resistant to this type of stress impact.     

Response of microbial communities of Lake Baikal to extreme temperatures

The survival rate, metabolic activity, and ability for growth of microbial communities of Lake Baikal after exposure to extremely low temperatures (freeze-thawing) for different lengths of time have been first studied. It has been shown that short-term freezing (1-3 days) inhibits the growth and activity of microbial communities. The quantity of microorganisms increased after 7- and 15-day freezing. In the periods of maximums, the total number of microorganisms in the test samples was twice as high as in the control. It was established that after more prolonged freezing the microorganisms required more time after thawing to adapt to new conditions. In the variants with 7- and 15-day freezing, the activities of defrosted microbial communities were three or more times higher than in the control. The survival rate and activity of Baikal microorganisms after freeze-thawing confirms the fact that the Baikal microbial communities are highly resistant to this type of stress impact.     

Domestication of honey bees was associated with expansion of genetic diversity

Humans have been keeping honey bees, Apis mellifera, in artificial hives for over 7000 years. Long enough, one might imagine, for some genetic changes to have occurred in domestic bees that would distinguish them from their wild ancestors. Indeed, some have argued that the recent mysterious and widespread losses of commercial bee colonies, are due in part to inbreeding. In this issue of Molecular Ecology, Harpur et al. (2012) show that the domestication of honey bees, rather than reducing genetic variance in the population, has increased it. It seems that the commercial honey bees of Canada are a mongrel lot, with far more variability than their ancestors in Europe.     

Use of human-made nesting structures by wild bees in an urban environment

Most bees display an array of strategies for building their nests, and the availability of nesting resources plays a significant role in organizing bee communities. Although urbanization can cause local species extinction, many bee species persist in urbanized areas. We studied the response of a bee community to winter-installed human-made nesting structures (bee hotels and soil squares, i.e. 0.5 m deep holes filled with soil) in urbanized sites. We investigated the colonization pattern of these structures over two consecutive years to evaluate the effect of age and the type of substrates (e.g. logs, stems) provided on colonization. Overall, we collected 54 species. In the hotels, two gregarious species, Osmia bicornis L. and O. cornuta Latr. dominated the community (over 87 % of the data). Over 2 years, the age of the soil squares did not affect their level of colonization and the same was true for the hotels with respect to O. bicornis and ‘other species’. However, O. cornuta occurred less often and raised fewer descendants in 1-year old hotels than in new ones. Bee nesting was not affected by the soil texture and, among above-ground nesting bees, only O. bicornis showed a preference for some substrates, namely Acer sp. and Catalpa sp. In a context of increasing urbanization and declining bee populations, much attention has focused upon improving the floral resources available for bees, while little effort has been paid to nesting resources. Our results indicate that, in addition to floral availability, nesting resources should be taken into account in the development of urban green areas to promote a diverse bee community.     

Fruit set of highland coffee increases with the diversity of pollinating bees

The worldwide decline of pollinators may negatively affect the fruit set of wild and cultivated plants. Here, we show that fruit set of the self-fertilizing highland coffee (Coffea arabica) is highly variable and related to bee pollination. In a comparison of 24 agroforestry systems in Indonesia, the fruit set of coffee could be predicted by the number of flower-visiting bee species, and it ranged from ca. 60% (three species) to 90% (20 species). Diversity, not abundance, explained variation in fruit set, so the collective role of a species-rich bee community was important for pollination success. Additional experiments showed that single flower visits from rare solitary species led to higher fruit set than with abundant social species. Pollinator diversity was affected by two habitat parameters indicating guild-specific nesting requirements: the diversity of social bees decreased with forest distance, whereas the diversity of solitary bees increased with light intensity of the agroforestry systems. These results give empirical evidence for a positive relationship between ecosystem functions such as pollination and biodiversity. Conservation of rainforest adjacent to adequately managed agroforestry systems could improve the yields of farmers.     

Response of five insect herbivores to multiple allelochemicals under fluctuating temperatures

Analysis of the combined effects of allelochemicals on insect herbivores is useful because there may be adverse additive or even synergistic effects. Analysis of the simultaneous effects of temperature and alleochemicals is also necessary because these factors may interact. We examined the effects of three allelochemicals found in tomato (chlorogenic acid, rutin and tomatine) and thermal regime (21:10 °C and 26:15 °C, representing spring and summer respectively) on five insect herbivores (a Solanaceae specialist, Manduca sexta, and the polyphagous Heliothis virescens, Pseudoplusia includens, Spodoptera frugiperda and Trichoplusia ni). There were allelochemical interactions and thermal regime-allelochemical interactions for all species, and so the patterns were complex. In some cases, paired allelochemicals or the combination of three allelochemicals showed adverse additive effects on insect performance. But that was not always the case, and there were only a few examples of synergism. Negative effects of the allelochemicals were sometimes, but not always, damped by the cooler thermal regime. Comparing the growth rates of the five species in this study with those of a previous study (a total of seven species) revealed five patterns. For two of three pairs of closely-related species, the paired species had distinctly different patterns. For example, for H. virescens, tomatine prevented development and chlorogenic acid slowed growth, whereas for Helicoverpa zea, tomatine just slowed growth and the phenolics had little effect. The specialist Manduca sexta had a pattern that was midway between patterns of the generalists; it was not the most tolerant of the allelochemicals.     

NMR and water relaxation of floral honey samples from wild and domesticated bees

The aqueous solutions of Bashkir floral honey of wild and domesticated bees were studied with high-resolution ¹H and ¹³C NMR and nuclear magnetic relaxation. NMR was shown to provide only qualitative data on the composition of the studied honey samples. Data on the composition of the minor components (amino acids), as well as the mobility of water protons in honey, indicate that the distinctions between honey from wild and domesticated bees are due to both the honey composition and the difference in the interactions of components with one another and with water.     

Fecal bacterial diversity in a wild gorilla

We describe the bacterial diversity in fecal samples of a wild gorilla by use of a 16S rRNA gene clone library and terminal-restriction fragment length polymorphism (T-RFLP). Clones were classified as Firmicutes, Verrucomicrobia, Actinobacteria, Lentisphaerae, Bacteroidetes, Spirochetes, and Planctomycetes. Our data suggest that fecal populations did not change temporally, as determined by T-RFLP.     

Response of traplining bumble bees to competition experiments: shifts in feeding location and efficiency

Summary In field experiments, we mapped the regular foraging routes (traplines) of marked bumble bees visiting Aralia hispida. When other bees were removed to create localized competitive vacuums, the marked bees shifted their feeding activity toward the removal areas. Bees foraging in these competitive vacuums probed more flowers per inflorescence than control bees. One bee's foraging was studied intensively before and after its local competitors were removed. Compared to four nestmates foraging elsewhere, the focal bee's trip times were shorter (p<0.005) and its food collection rate was marginally higher (P=0.064) during the removal, although all the bees foraged similarly before the removal. These observations indicate that traplining bumble bees opportunistically modify their use of space in response to the activities of other bees in a highly competitive environment.     

Genetic diversity in wild populations of Paulownia fortunei

The genetic diversities of 16 Paulownia fortunei populations involving 143 individuals collected from 6 provinces in China were analyzed using amplified fragment length polymorphism (AFLP). A total of 9 primer pairs with 1169 polymorphic loci were screened out, and each pair possessed 132 bands on average. The percentage of polymorphic bands (98.57%), the effective number of alleles (1.2138–1.2726), Nei’s genetic diversity (0.1566–0.1887), and Shannon’s information index (0.2692–0.3117) indicated a plentiful genetic diversity and different among Paulownia fortune populations. The genetic differentiation coefficient between populations was 0.2386, while the gene flow was 1.0954, and the low gene exchange promoted genetic differentiation. Analysis of variance indicated that genetic variation mainly occurred within populations (81.62% of total variation) rather than among populations (18.38%). The 16 populations were divided by unweighted pair-group method with arithmetic means (UPGMA) into 4 groups with obvious regionalism, in which the populations with close geographical locations (latitude) were clustered together.