Genetic structure of drone congregations of the stingless bee Scaptotrigona mexicana

Drones of stingless bee species often form distinctive congregations of up to several hundred individuals which can persist over considerable periods of time. Here we analyse the genetic structure of three drone congregations of the neotropical stingless bee Scaptotrigona mexicana employing eight microsatellite markers. Two congregations were close to each other (50 m), the third one was located more than 10 km away from them. This spatial pattern was also reflected on the genetic level : the two close congregations did not show any population sub-structuring, whereas the more distant congregation showed a significant population differentiation to both of them. Population subdifferentiation was however low with F _st values (F _st = 0.020 and 0.014) between the distant congregations, suggesting gene flow over larger distances mediated by the drones of S. mexicana. Based on the genotypic data we also estimated the number of colonies contributing drones to the congregations. The two joint congregations consisted of drones originating from 39,6 colonies, while the third congregation was composed of drones from 21,8 colonies, thus proving that congregations of S. mexicana are constituted of unrelated drones of multicolonial origin. Received 23 April 2007; revised 21 September 2007; accepted 2 October 2007.     

Foragers of the stingless bee Plebeia droryana inform nestmates about the direction,but not the distance to food sources

1. The tropical stingless bees have evolved intricate communication systems to recruit nestmates to food locations. Some species are able to accurately communicate the location of food, whereas others simply announce the presence of food in the environment.
2. Plebeia droryana is a tiny Neotropical stingless bee that, until recently, was thought to use a solitary foraging strategy, that is without the use of a recruitment communication system. However, recent research has indicated that P. droryana might be able to recruit nestmates to specific food source locations.
3. We tested this by studying whether foragers can guide nestmates in the direction and the distance of artificial feeders placed in the vicinity of the colony. We trained bees to a scented sucrose solution feeder at 10 m and placed different feeders either in different directions (experiment 1) or in different distances (experiment 2). We found that P. droryana directs newcomers in the right direction, but distance information does not seem to be communicated.
4. Moreover, we then tested whether newcomers use chemical and visual cues originating from nestmates foraging at the food source, but found no evidence for the use of these social cues provided by conspecifics.
5. The potential mechanism that P. droryana may use to orient recruits toward the food source, however, remains unknown and requires further study.

     

The use of field–based social information in eusocial foragers: local enhancement among nestmates and heterospecifics in stingless bees

Abstract. 1. Foragers of social insects can be guided to profitable food sources by social information transfer within the nest. This study showed that in addition to such an information-centre strategy, social information in the field also plays an important role in individual foraging decisions. The effect of the presence of a nestmate on individual decision-making on where to forage was investigated in six species of stingless bee that differ in their recruitment system. Some species preferred to feed close to a nestmate (local enhancement) whereas other species actively avoided landing close to a nestmate. The term local inhibition is introduced for this avoidance behaviour.
2. Local enhancement and local inhibition were species specific but were not related to the species' recruitment system.
3. Local enhancement and local inhibition were affected by the individual's experience with the food source. Newly recruited foragers of Trigona amalthea showed local enhancement whereas experienced foragers showed local inhibition.
4. These individual decision-making rules explained accurately the spatial distribution of recruited nestmates: foraging groups of T. amalthea , which shows local inhibition, were more dispersed than foraging groups of Oxytrigona mellicolor , which shows local enhancement.
5. The effect of heterospecifics on stingless bee flower choice was investigated for 18 species combinations. Landing decisions were influenced significantly by the aggressiveness and the body size of the resident bee. Larger and more aggressive heterospecifics were avoided, whereas in some cases less aggressive bees acted as an attraction cue.     

A study of the antidiarrheal properties of Loeselia mexicana on mice and rats

Antidiarrheal properties of hexane, chloroform, methanol and aqueous extracts from Loeselia mexicana were studied using mice and rats as animal models. Flavones and sesquiterpenlactones were detected in the chemical screening of the aqueous extract. Diarrhea was induced by castor oil or MgSO4. The methanol extract diminished diarrhea in mice induced by MgSO4, while the aqueous extract showed an effect on castor-oil-induced. The aqueous extract also reduced castor-oil-enhanced intestinal transit and inhibited defecation of normal mice. The results obtained showed a symptomatic relief of diarrhea.     

多花刺槐花粉与柱头形态及授粉亲和性研究

运用扫描电子显微镜对多花刺槐不同发育时期的花粉与柱头形态进行观察分析;采用人工控制授粉方法,将多花刺槐花粉分别与异株多花刺槐和刺槐优良无性系(‘鲁刺152’)授粉,并用苯胺蓝试剂染色法观察多花刺槐花粉管的萌发过程,分析其授粉亲和性,以探究多花刺槐自然结实率低的原因,为多花刺槐杂交育种提供理论依据。结果表明:(1)多花刺槐花粉粒大小平均为32.08μm×19.55μm(极轴长×赤道轴长),形状为长椭球形、略方,具3个萌发沟,花粉粒大小在开花当时(花朵旗瓣微微张开,花药开始散粉)达到最大(33.71μm×20.11μm),且形状饱满,此时为采粉的最佳时间。(2)柱头表面具粘液和凸起,开花前12h可授性最好,开花后48h柱头开始分解,可授性已很差;柱头的可授期从开花前24h至开花后24h,约为3d。(3)多花刺槐花粉在异株多花刺槐和‘鲁刺152’为母本的植株上均可萌发,并伸长至子房,但在前者的柱头上萌发较晚,伸长速度较慢,说明它们之间均具有亲和性,但与异株多花刺槐的亲和性较差。     

Caste-specific modulation of juvenile hormone III content and ecdysteroid titer in postembryonic development of the stingless bee,Scaptotrigona postica depilis

Summary Juvenile hormone III content and ecdysteroid titer were analyzed for larval and pupal development of the stingless bee,Scaptotrigona postica depilis. Castespecific differences in juvenile hormone III content were detected at three developmental phases: at the transition from the fourth to the fifth larval stadium, in the spinning phase of the fifth larval stadium, and shortly after the imaginal moult. During the fifth larval stadium, juvenile hormone content closely reflects corpora allata activity. Juvenile hormone synthesis may thus be responsible for the elevated hormone titer in spinning-phase queen larvae, a phase of known sensitivity for induction of queen characters by exogenous juvenile hormone. For ecdysteroids, two phases of caste-specific differences were found: in the pre-pupal phase, and shortly after the imaginal moult. In both periods the titer in queens is distinctly higher compared to workers.Abbreviations Im imago 1 day after eclosion - L3, L4, L5 larval instars 3, 4, and 5 - L5F1, L5F2 substages of feeding phase in fifth larval instar - L5S1, L5S2, L5S3 substages of spinning phase in fifth larval instar - PP1, PP2 substages of prepupal phase - Pw white eyed pupa - Pp pink eyed pupa - Pr red eyed pupa - Pd dark eyed pupa - Pdl, Pdm, Pdd dark eyed pupa with progressive tanning of cuticle - RIA radioimmunoassay     

An exploration of the relationship between recruitment communication and foraging in stingless bees

Social information is widely used in the animal kingdom and can be highly adaptive. In social insects, foragers can use social information to find food, avoid danger, or choose a new nest site. Copying others allows individuals to obtain information without having to sample the environment. When foragers communicate information they will often only advertise high-quality food sources, thereby filtering out less adaptive information. Stingless bees, a large pantropical group of highly eusocial bees, face intense inter- and intra-specific competition for limited resources, yet display disparate foraging strategies. Within the same environment there are species that communicate the location of food resources to nest-mates and species that do not. Our current understanding of why some species communicate foraging sites while others do not is limited. Studying freely foraging colonies of several co-existing stingless bee species in Brazil, we investigated if recruitment to specific food locations is linked to 1) the sugar content of forage, 2) the duration of foraging trips, and 3) the variation in activity of a colony from 1 day to another and the variation in activity in a species over a day. We found that, contrary to our expectations, species with recruitment communication did not return with higher quality forage than species that do not recruit nestmates. Furthermore, foragers from recruiting species did not have shorter foraging trip durations than those from weakly recruiting species. Given the intense inter- and intraspecific competition for resources in these environments, it may be that recruiting species favor food resources that can be monopolized by the colony rather than food sources that offer high-quality rewards.     

Thorax vibrations of a stingless bee (<Emphasis Type="Italic">Melipona seminigra</Emphasis>). I. No influence of visual flow

An important question in stingless bee communication is whether the thorax vibrations produced by foragers of the genus Melipona upon their return to the nest contain spatial information about food sources or not. As previously shown M. seminigra is able to use visual flow to estimate flight distances. The present study investigated whether foraging bees encode the visually measured distance in their thorax vibrations. Bees were trained to collect food in flight tunnels lined with a black-and-white pattern on their side walls and floor, which substantially influenced the image motion they experienced. When the bees had collected inside the tunnels the temporal pattern of their vibrations differed significantly from the pattern after collecting in a natural environment. These changes, however, were not associated with the visual flow experienced inside the tunnel. Bees collecting in tunnels offering little visual flow (stripes parallel to flight direction) modified their vibrations similarly to bees collecting in tunnels with high image motion (cross stripes). A higher energy expenditure due to drastically reduced flight velocities inside the tunnel is suggested to be responsible for changes in the thorax vibrations. The bees' vibrations would thus reflect the overall energetic budget of a foraging trip.     

Use of visual loop-mediated isotheral amplification of rimM sequence for rapid detection of Mycobacterium tuberculosis and Mycobacterium bovis

Mycobacterium tuberculosis and Mycobacterium bovis are pathogenic bacterial species in the genus Mycobacterium and the causative agents of most cases of tuberculosis (TB). Detection of M. tuberculosis and M. bovis using conventional culture- and biochemical-based assays is time-consuming and laborious. Therefore, a simple and sensitive method for rapid detection has been anxiously awaited. In the present study, a visual loop-mediated isothermal amplification (LAMP) assay was designed from the rimM (encoding 16S rRNA-processing protein) gene sequence and used to rapidly detect M. tuberculosis and M. bovis from clinical samples in South China. The visual LAMP reaction was performed by adding calcein and manganous ion, allowing the results to be read by simple visual observation of color change in a closed-tube system, and which takes less than 1 h at 65 °C. The assay correctly identified 84 M. tuberculosis isolates, 3 M. bovis strains and 1 M. bovis BCG samples, but did not detect 51 non-tuberculous mycobacteria (NTM) isolates and 8 other bacterial species. Sensitivity of this assay for detection of genomic DNA was 1 pg. Specific amplification was confirmed by the ladder-like pattern of gel electrophoresis and restriction enzyme HhaI digestion. The assay successfully detected M. tuberculosis and M. bovis not only in pure bacterial culture but also in clinical samples of sputum, pleural fluid and blood. The speed, specificity, sensitivity of the rimM LAMP, the lack of a need for expensive equipment, and the visual readout show great potential for clinical detection of M. tuberculosis and M. bovis.     

Thorax vibrations of a stingless bee (<Emphasis Type="Italic">Melipona seminigra</Emphasis>). II. Dependence on sugar concentration

Using a laser vibrometer we studied the influence of the foods sugar concentration on different parameters of the thorax vibrations produced by foragers of Melipona seminigra during trophallaxis in the nest. The concentrations tested (20–70% sugar w/w) were within the biologically relevant range. They substantially influenced different parameters of the thorax vibrations. An increase of energy gains at the food source due to an increased sugar concentration was followed by an increase of both the pulse duration and the duty cycle and by a decrease of the pause duration between two subsequent pulses. These findings further support the hypothesis that the temporal pattern of the thorax vibrations reflects the energy budget of a foraging trip rather than food source distance. Likewise, the steep increase of pulse duration variability with sugar concentration is hard to reconcile with the assumption that pulse duration conveys reliable information about food source distance when bees collect at high-quality food sources.     

The phylogenetic placement of the Leucogastrales, including Mycolevis siccigleba (Cribbeaceae), in the Albatrellaceae using morphological and molecular data

The morphology of many hypogeous fungi converges on a homogeneous reduced form, suggesting that disparate lineages are subject to a uniform selection pressure. The primary goal of this study was to evaluate the morphology and infer the phylogeny of the Leucogastrales with Mycolevis siccigleba using a Bayesian methodology. A comprehensive morphological assessment was used for an a priori phylogenetic inference to guide the sequencing effort. All structures except spore ornamentation pointed to the Albatrellaceae as the most likely sister taxon. Polyporoletus sublividus, a close relative of Albatrellus, produces ornamented basidiospores with a similar structure to M. siccigleba basidiospores. The ITS from 30 taxa was used for the molecular phylogenetic analysis. P. sublividus was found sister to Mycolevis. Leucophleps spinispora and L. magnata formed a group sister to the Polyporoletus/Mycolevis group, whereas Leucogaster was polyphyletic with respect to the core of the Leucogastrales and sister to A. caeruleoporus. This relationship was expected as previously undescribed chlamydospores produced by members of Albatrellus had a similar morphology to the basidiospores of L. rubescens.     

Honeydew feeding in the solitary bee Osmia bicornis as affected by aphid species and nectar availability

Like honey bees (Apis mellifera), non-Apis bees could exploit honeydew as a carbohydrate source. In addition to providing carbohydrates, this may expose them to potentially harmful plant products secreted in honeydew. However, knowledge on honeydew feeding by solitary bees is very scarce. Here we determine whether the polylectic solitary bee Osmia bicornis (=O. rufa) collects honeydew under semi-field conditions, and whether this is affected by aphid species and presence of floral nectar. Bees were provided with oilseed rape plants containing flowers and/or colonies of either Myzus persicae or Brevicoryne brassicae. We used the total sugar level of the bee crop as a measure of the individual's nutritional state and the oligosaccharide erlose as indicator for honeydew consumption. Erlose was present in honeydews from both aphid species, while absent in oilseed rape nectar, nor being synthesized by O. bicornis. When bees were confined to a single honeydew type as the only carbohydrate source, consumption of M. persicae honeydew was confirmed for 47% of the bees and consumption of B. brassicae honeydew for only 3%. Increased mortality in the latter treatment provided further evidence that B. brassicae honeydew is an unsuitable food source for O. bicornis. All bees that were given the choice between honeydew and floral nectar showed significantly increased total sugar levels. However, the fact that no erlose was detected in these bees indicates that honeydew was not consumed when suitable floral nectar was available. This study demonstrates that honeydew exploitation by O. bicornis is dependent on honeydew type and the presence of floral nectar.     

Phylogeographic patterns in Leccinum sect. Scabra and the status of the arctic-alpine species L. rotundifoliae

We investigated inter- and intraspecific phylogenetic relationships in the ectomycorrhizal fungal genus Leccinum section Scabra. Species of this section are exclusively associated with Betula and occur throughout the Northern Hemisphere. We compared the phylogenetic relationships of arctic, alpine, boreal and temperate accessions of section Scabra based on DNA sequences of the single-copy nuclear gene Gapdh and the multiple-copy nuclear region 5.8S-ITS2. Exclusively arctic lineages were not detected in species that occur both in arctic-alpine or boreal regions, except in L. rotundifoliae that was restricted to cold climates. L. scabrum and L. holopus showed an intercontinental phylogeographic pattern, and L. variicolor showed a pattern unrelated to geographical distribution. Molecular clock estimates indicated that L. rotundifoliae is as old as other species in section Scabra. Individual gene trees suggest that interspecific hybridisation occurred several times in the evolution of section Scabra.