The importance of plant diversity in maintaining the pollinator bee, Eulaema nigrita (Hymenoptera: Apidae) in sweet passion fruit fields

The euglossine bee Eulaema nigrita plays an important role for the pollination of native and economically important plants, such as the sweet passion-fruit Passiflora alata. E. nigrita uniquely collects the nectar from the flowers of P alata, nevertheless, it needs to visit other plants to collect pollen, nectar and other resources for its survival. There are two methods to identify the species of plants used by bees in their diet: by direct observation of the bees in the flowers, and through identification of pollen grains present in brood cells, feces, or in the bees' body. In order to identify the other plants that E. nigrita visits, we analyzed samples of pollen grains removed from the bee's body in the course of the flowering period of P alata. Among our results, the flora visited by E. nigrita comprised 40 species from 32 genera and 19 families, some of them used as a pollen source or just nectar. In spite of being a polyletic species, E. nigrita exhibited preference for some plant species with poricidal anthers. P alata which has high sugar concentration nectar was the main source of nectar for this bee in the studied area. Nonetheless, the pollinic analysis indicated that others nectariferous plant species are necessary to keep the populations of E. nigrita. Studies such as this one are important since they indicate supplementary pollen-nectar sources which must be used for the conservation of the populations of E. nigrita in crops neighbouring areas. In the absence of pollinators, growers are forced to pay for hand pollination, which increases production costs; keeping pollinators in cultivated areas is still more feasible to ensure sweet passion fruit production. Rev. Biol. Trop. 60 (4): 1553-1565. Epub 2012 December 01.

Compared morphology of the immatures of males of two urban ant species of Camponotus

The immatures of males of two species of Camponotus ants (Hymenoptera: Formicidae) are described and compared by light and electron microscopy. The numbers of larval instars were determined: Camponotus rufipes Fabricius (Hymenoptera: Formicidae) have four instars; and Camponotus vittatus Forel have three. Male larvae of the two species are similar to previously described Camponotus larvae, sharing the following traits: basic shape of body and mandible, presence of 'chiloscleres', 'praesaepium' (some specimens), labial pseudopalps, and ten pairs of spiracles. However, larvae of the two species can be separated by bodily dimensions and based on their hair number and types. Worker larvae of C. vittatus previously described are extensively similar to male larvae, with only a few inconspicuous differences that may result from intraspecific variation or sexual differences.

Mixed colonies of two species of congeneric stingless bees (Hymenoptera: Apinae, Meliponini) display environmentally-acquired and endogenously-produced recognition signals

Nestmate recognition is fundamental for the maintenance of social organization in insect nests. It is becoming well recognized that cuticle hydrocarbons mediate the recognition process, although the origin of recognition cues in stingless bees remains poorly explored. The present study investigates the effects of endogenously-produced and environmentally-acquired components in cuticular hydrocarbons in stingless bees. The tests are conducted using colonies of Plebeia droryana Friese and Plebeia remota Holmberg. Recognition tests are performed with four different groups: conspecific nestmates, conspecific non-nestmates, heterospecifics and conspecific, genetically-related individuals that emerge in a heterospecific nest. This last group is produced by introducing brood cells of P. droryana into a P. remota colony, and the resulting adult bees are tested for acceptance 10 days after emergence. For all groups, 15 individuals are sampled for chemical analysis. The results show the acceptance of all conspecific nestmates, and the rejection of almost every conspecific non-nestmate and every heterospecific bee. Genetically-related individuals emerging from heterospecific nests present intermediate rejection (66.7% rejection). Chemical analysis shows that P. droryana individuals emerging in a P. remota nest have small amounts of alkene and diene isomers found in P. remota cuticle that are not found in workers from the natal nest. The data clearly show that the majority of the compounds present in P. droryana cuticle are endogenously produced, although a few unsaturated compounds are acquired from the environment, increasing the chemical differences and, consequently, the rejection percentages.

Vitellogenin content in fat body and ovary homogenates of workers and queens of Melipona quadrifasciata anthidioides during vitellogenesis

Vitellogenin (Vg) is an egg yolk protein that is produced primarily in the fat body of most female insects. In the advanced social structure of eusocial honeybees, the presence of the queen inhibits egg maturation in the workers ovaries. However in the stingless bee Melipona quadrifasciata, the workers always develop ovaries and lay a certain amount of eggs while provisioning the brood cells with larval food during what is known as the worker nurse phase. The present work is a comparative study of the presence of Vg in homogenates of the fat bodies and ovaries of the nurse workers, and the virgin and physogastric queens of M. quadrifasciata. The presence of Vg was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoblotting using Apis mellifera anti-egg antibody. Vg was not detected in the fat bodies or ovaries of the workers, but it was found in the ovaries of virgin and physogastric queens and in the fat body of physogastric queens. The results are discussed, taking into account the reproductive state of the individuals and the other possible roles of Vg, such as a storage protein for metoabolism of other organs.

First report of sacbrood virus in honey bee (Apis mellifera) colonies in Brazil

Sacbrood disease, an affliction of honey bees (Apis mellifera) characterized by brood that fails to pupate and subsequently dies, is an important threat to honey bee health. The disease is caused by the sacbrood virus (SBV), a positive-, single-stranded RNA virus in the order Picornavirales. Because of the economic importance of honey bees for both pollination and honey production, it is vital to understand and monitor the spread of viruses such as SBV. This virus has been found in many places across the globe, including recently in some South American countries, and it is likely that it will continue to spread. We performed a preliminary study to search for SBV in two apiaries of Africanized honey bees in the State of Sao Paulo, Brazil, using RT-PCR and Sanger sequencing and found the first evidence of SBV in honey bee colonies in Brazil. The virus was detected in larvae, foraging and nurse bees from two colonies, one of which had symptoms of sacbrood disease, at the beginning of the winter season in June 2011. No SBV was found in samples from nine other nearby colonies.

Cell-sealing efficiency and reproductive workers in the species Melipona bicolor (Hymenoptera, Meliponini): double standard and possible rogue conduct

In many hymenopteran insect societies, selfish workers are policed, as selfishness can negatively affect the average inclusive fitness of one or both castes by reducing either the degree of average relatedness to the colony's male offspring or colony efficiency. In stingless bees, the rapid capping of brood cells could aid in controlling selfishness; to this end, we studied cell-sealing efficacy in Melipona bicolor. Execution of cell sealing was found to be both rapid and almost continuous. Comparing the performance of reproductive and non-reproductive workers, the former sealed the cells more efficiently when they contained their own eggs, but less so when the queens' eggs were involved. We argue that the occurrence of disruptions in cell sealing through self-serving reproductive workers is capable of undermining sealing efficacy as a policing instrument, thus making reproductive workers potential rogue individuals.

Cuticular Hydrocarbon Variation of Castes and Sex in the Weaver Ant Camponotus textor (Hymenoptera: Formicidae)

Cuticular hydrocarbons play important roles as chemical signatures of individuals, castes, sex and brood. They also can mediate the regulation of egg laying in ants, by informing directly or indirectly the reproductive status of queens. In this study we asked whether cuticular hydrocarbon profiles are correlated with castes and sex of Camponotus textor. Cuticular hydrocarbons were extracted from part of a mature colony (80 workers, 27 major workers, 27 queens, 27 virgin queens and 27 males). Results showed that cuticular hydrocarbons varied quantitatively and qualitatively among the groups and this variation was sufficiently strong to allow separation of castes and genders. We discuss the specificity of some compounds as possible regulatory compounds of worker tasks and reproduction in C. textor.

The influence of individual and colony level variation in behavior on colony performance in ants

In my dissertation I investigated the influence of behavioral variation between and within ant colonies on group performance. In particular, I analyzed how evolution shapes behavior in response to ecological conditions, and whether within-group diversity improves productivity as suggested by theory. Our field and laboratory experiments showed that behavioral diverse groups are more productive. Different aggression levels within colonies were beneficial under competitive field situations, whereas diversity in brood care and exploratory behavior were favored in non-competitive laboratory situations. We then examined whether population density and social parasite presence shape aggression through phenotypic plasticity and/or natural selection. The importance of selection was indicated by the absence of density or parasite effects on aggression in a field manipulation. Indeed, more aggressive colonies fared better under high density and during parasite attack. When analyzing the proximate causes of individual behavioral variation, ovarian development was shown to be linked to division of labor and aggressiveness. Finally, our studies show that differences in the collective behavior can be linked to immune defense and productivity. My dissertation demonstrates that behavioral variation should be studied on multiple scales and when possible combined with physiological analyses to better understand the evolution of animal personalities in social groups.rn

Entwicklung einer Kryokonservierungsmethode für Spermien der Honigbiene, Apis mellifera

Die westliche Honigbiene (Apis mellifera) ist von großer ökologischer und ökonomischer Bedeutung. Seit Jahren zeichnen sich in Nordamerika sowie in manchen Teilen Europas rückläufige Bienenvölkerzahlen und eine abnehmende Artenvielfalt innerhalb der Bienenfamilie ab. Mittlerweile ist von einer globalen Bestäuberkrise die Rede und es wird verstärkt nach Möglichkeiten gesucht, um dieser Krise entgegenzuwirken. Eine Konservierung von Bienenspermien in flüssigem Stickstoff ohne Fruchtbarkeitsreduzierung würde die Bienenzucht revolutionieren und stark beschleunigen, da räumliche und zeitliche Restriktionen bei der Wahl des Bienenspermas wegfielen. Zudem wäre eine Möglichkeit zur Sicherung der genetischen Diversität geschaffen. Im Rahmen des hier vorgestellten Projektes wurde eine solche Methode erarbeitet. In umfangreichen Abkühl- und Einfrierversuchen konnte eine neue Konservierungstechnik entwickelt werden, bei der das Kryoprotektivum mittels Dialyse dem Bienensperma zugesetzt wird. Dieses Verfahren erhält die native Spermaform, in der die Spermien parallel und inaktiv in dicht gepackten Clustern vorliegen, und erzielt bisher unerreichte Besamungserfolge. So konnten durchschnittlich 1,25 Mio. Spermien in den Spermatheken besamter Königinnen gezählt werden und davon waren ungefähr 90% motil. Besonders vielversprechend ist jedoch, dass 79,4% der Brut weiblich waren. Ein so hoher Anteil weiblicher Brut konnte bislang nicht erreicht werden und wäre für züchterische Zwecke ausreichend.

Dissecting Carotenoid from Structural Components of Carotenoid-Based Coloration: A Field Experiment with Great Tits (Parus major)

Carotenoid-based yellowish to red plumage colors are widespread visual signals used in sexual and social communication. To understand their ultimate signaling functions, it is important to identify the proximate mechanism promoting variation in coloration. Carotenoid-based colors combine structural and pigmentary components, but the importance of the contribution of structural components to variation in pigment-based colors (i.e., carotenoid-based colors) has been undervalued. In a field experiment with great tits (Parus major), we combined a brood size manipulation with a simultaneous carotenoid supplementation in order to disentangle the effects of carotenoid availability and early growth condition on different components of the yellow breast feathers. By defining independent measures of feather carotenoid content (absolute carotenoid chroma) and background structure (background reflectance), we demonstrate that environmental factors experienced during the nestling period, namely, early growth conditions and carotenoid availability, contribute independently to variation in yellow plumage coloration. While early growth conditions affected the background reflectance of the plumage, the availability of carotenoids affected the absolute carotenoid chroma, the peak of maximum ultraviolet reflectance, and the overall shape, that is, chromatic information of the reflectance curves. These findings demonstrate that environment-induced variation in background structure contributes significantly to intraspecific variation in yellow carotenoid-based plumage coloration.

Effect of sibling competition and male carotenoid supply on offspring condition and oxidative stress

Early developmental conditions have major implications for an individual's fitness. In species where offspring are born simultaneously, the level of sibling competition for food access is intense. In birds, high sibling competition may subject nestlings to decreased growth rate as a result of limited food and increased levels of oxidative stress through high metabolic activity induced by begging behaviors. We manipulated the level of sibling competition in a natural population of great tits and assessed the consequences for nestling body condition and resistance to oxidative stress. In a full factorial design, we both augmented brood size to increase sibling competition and supplemented the male parents with physiological doses of carotenoids thereby doubling the natural carotenoid intake, aiming at increasing the males' investment in current reproduction and thereby decreasing sibling competition. Nestling body mass was reduced by the brood enlargement and enhanced by the carotenoid supplementation of fathers. Nestling resistance to oxidative stress, measured as total antioxidant defenses in whole blood, was not influenced by the treatments. Because nestlings experience high metabolic activities, an absence of an effect of sibling competition on free radicals production seems unlikely. Nestling body mass decreased and resistance to oxidative stress tended to increase with initial brood size, and hence these correlational effects suggest a trade-off between morphological growth and development of the antioxidant system. However, the result of the experimental treatment did not support this trade-off hypothesis. Alternatively, it suggests that nestling developed compensatory mechanisms that were not detected by our antioxidant capacity measure.

Small hive beetles, Aethina tumida, are vectors of Paenibacillus larvae

The transmission of honeybee pathogens by free-flying pests, such as small hive beetles (=SHB), would be independent of bees and beekeepers and thereby constitute a new challenge for pathogen control measures. Here we show that larval and adult SHB become contaminated with Paenibacillus larvae spores when exposed to honeybee brood combs with clinical American foulbrood (=AFB) symptoms in the laboratory. This contamination persists in pupae and newly emerged adults. After exposure to contaminated adult SHB, honeybee field colonies showed higher numbers of P. larvae spores in worker and honey samples after five weeks. Despite these results, the rather low number of P. larvae spores on adult SHB suggests that clinical AFB outbreaks are not likely. However, even small spore numbers can be sufficient to spread P. larvae. Therefore, our data clearly show that SHB are vectors of P. larvae. We suggest considering the role of SHB in AFB control in areas where both pests are established.

Patterns of functional enzyme activity in fungus farming ambrosia beetles

Introduction In wood-dwelling fungus-farming weevils, the so-called ambrosia beetles (Curculionidae: Scolytinae and Platypodinae), wood in the excavated tunnels is used as a medium for cultivating fungi by the combined action of digging larvae (which create more space for the fungi to grow) and of adults sowing and pruning the fungus. The beetles are obligately dependent on the fungus that provides essential vitamins, amino acids and sterols. However, to what extent microbial enzymes support fungus farming in ambrosia beetles is unknown. Here we measure (i) 13 plant cell-wall degrading enzymes in the fungus garden microbial consortium of the ambrosia beetle Xyleborinus saxesenii, including its primary fungal symbionts, in three compartments of laboratory maintained nests, at different time points after gallery foundation and (ii) four specific enzymes that may be either insect or microbially derived in X. saxesenii adult and larval individuals. Results We discovered that the activity of cellulases in ambrosia fungus gardens is relatively small compared to the activities of other cellulolytic enzymes. Enzyme activity in all compartments of the garden was mainly directed towards hemicellulose carbohydrates such as xylan, glucomannan and callose. Hemicellulolytic enzyme activity within the brood chamber increased with gallery age, whereas irrespective of the age of the gallery, the highest overall enzyme activity were detected in the gallery dump material expelled by the beetles. Interestingly endo-β-1,3(4)-glucanase activity capable of callose degradation was identified in whole-body extracts of both larvae and adult X. saxesenii, whereas endo-β-1,4-xylanase activity was exclusively detected in larvae. Conclusion Similar to closely related fungi associated with bark beetles in phloem, the microbial symbionts of ambrosia beetles hardly degrade cellulose. Instead, their enzyme activity is directed mainly towards comparatively more easily accessible hemicellulose components of the ray-parenchyma cells in the wood xylem. Furthermore, the detection of xylanolytic enzymes exclusively in larvae (which feed on fungus colonized wood) and not in adults (which feed only on fungi) indicates that only larvae (pre-) digest plant cell wall structures. This implies that in X. saxesenii and likely also in many other ambrosia beetles, adults and larvae do not compete for the same food within their nests - in contrast, larvae increase colony fitness by facilitating enzymatic wood degradation and fungus cultivation.

Analysis of genetic parentage in the tawny owl (Strix aluco) reveals extra-pair paternity is low

We have investigated genetic parentage in a Swiss population of tawny owls (Strix aluco). To this end, we performed genetic analysis for six polymorphic loci of 49 avian microsatellite loci tested for cross-species amplification. We found one extra-pair young out of 137 (0.7%) nestlings in 37 families (2.7%). There was no intra-specific brood parasitism. Our results are in accordance with previous findings for other raptors and owls that genetic monogamy is the rule. Female tawny owls cannot raise offspring without a substantial contribution by their mates. Hence one favoured hypothesis is that high paternal investment in reproduction selects for behaviour that prevents cuckoldry.

Delayed dispersal as a potential route to cooperative breeding in ambrosia beetles

Abstract  Xyleborini are a species-rich tribe of ambrosia beetles, which are haplodiploid and typically mate among siblings within their natal brood chamber. Several characteristics of this tribe would predict the evolution of higher levels of sociality: high genetic relatedness within galleries due to inbreeding, high costs of dispersal and the potential benefit of cooperation in brood care within the natal gallery (e.g. by fungus gardening, gallery extension, offspring feeding and cleaning). However, information on the social system of these beetles is very limited. We examined the potential for cooperative breeding in Xyleborinus saxeseni by monitoring dispersal in relation to brood size and composition. Results show that adult female offspring delay dispersal despite dispersal opportunities, and apparently some females never disperse. The femalesâ?? decision to stay seems to depend on the presence of eggs and dependent siblings. We found no indication that female offspring reproduce in their natal gallery, as colonies with many mature daughters do not contain more eggs than those with few or no daughters. There is a significant positive relationship between the number of females present and the number of dependent siblings (but not eggs), which suggests that cooperative brood care of female offspring raises colony productivity by improving survival rates of immatures. Our results suggest that cooperative breeding is likely to occur in X. saxeseni and possibly other xyleborine species. We argue that a closer look at sociality within this tribe may yield important information on the factors determining the evolution of cooperative breeding and advanced social organization.