Effect of worker number and diapause duration on colony parameters of the bumblebee,Bombus terrestris (Hymenoptera: Apidae)

Bumblebee, Bombus terrestris queens undergo winter diapause and show a great difference in diapause duration in natural conditions. Queens emerged from diapause initiate colonies by producing a batch of diploid (fertilised) eggs that develop into workers. In this study we investigated the effects of both the duration of queen diapause (2, 3, 4, or 5 months) and colony size (artificially limited to 50, 100, 150, and 200 workers) on the number of sexuals (males or new queens — gynes) produced, when gynes are produced and the longevity of both the foundress queen and the colony. Both worker population and diapause duration showed significant effect on sexual gyne production, foundress queen longevity and colony longevity but their interaction effect was insignificant. The worker number and diapause duration, respectively showed significant effect on sexual male production and gyne emergence period, but their interaction effects were insignificant.     

乙基多杀菌素和联苯肼酯对地熊蜂的毒性及风险评估

【目的】明确乙基多杀菌素和联苯肼酯对地熊蜂Bombus terrestris的毒性, 探讨这两种农药亚致死浓度对地熊蜂体内乙酰胆碱酯酶(AchE)、谷胱甘肽-S-转移酶(GST)和羧酸酯酶(CarE) 3种解毒酶活性的影响。【方法】采用饲喂法测定60 g a.i./L乙基多杀菌素和43%联苯肼酯对地熊蜂采集蜂的急性经口毒性,依据农药对蜜蜂生态风险的危害熵(hazard quotient, HQ)值评估这两种农药对地熊蜂的风险。同时测定了这两种农药亚致死剂量(LD₅₀和LD₈₀)处理后地熊蜂AchE, GST和CarE的活性变化。【结果】60 g a.i./L乙基多杀菌素和43%联苯肼酯对地熊蜂采集蜂的急性经口毒性测定48 h时LD₅₀值分别为3.590和1 447 μg a.i./蜂,其中60 g a.i./L乙基多杀菌素表现为中毒,43%联苯肼酯表现为低毒。两种农药对地熊蜂采集蜂的HQ值均低于50,表现为低风险。LD₅₀和LD₈₀剂量的乙基多杀菌素处理组与对照组相比,3 h时地熊蜂AchE活性被激活,显著高于对照组(P＜0.05),分别为对照组的1.45和1.23倍,24 h后活性受到抑制,两个剂量处理组AchE活性均显著低于对照组(P＜0.05);CarE活性3 h时同样被激活,显著高于对照组(P＜0.05),LD₅₀和LD₈₀剂量处理组CarE活性分别为对照组的1.24和1.53倍, 24 h后活性受到抑制,其中LD₅₀剂量处理组CarE活性显著低于对照组(P＜0.05),LD₈₀剂量处理组CarE活性与对照组差异不显著(P＞0.05);LD₅₀和LD₈₀剂量处理组GST活性3 h被激活,显著高于对照组(P＜0.05),分别为对照组的2.24和2.58倍,24 h后活性降低,但两个剂量处理组GST活性仍显著高于对照组(P＜0.05)。43%联苯肼酯处理后,与对照组相比3 h时LD₅₀和LD₈₀剂量处理组AchE活性与对照组差异不显著(P＞0.05),24 h后AchE活性降低,显著低于对照组(P＜0.05),分别是对照组的75%和80%;CarE活性3 h时被抑制,LD₅₀剂量处理组CarE活性显著低于对照组(P＜0.05),LD₈₀剂量处理组CarE活性低于对照组,但差异不显著(P＞0.05),24 h后CarE活性被激活,其中LD₅₀剂量处理组CarE活性高于对照组,但差异不显著(P＞0.05),LD₈₀剂量处理组CarE活性显著高于对照组(P＜0.05);LD₅₀剂量处理组GST活性3 h时被激活,显著高于对照组(P＜0.05),24 h后活性降低,但仍显著高于对照组(P＜0.05),3 h和24 h的活性分别为对照组的2.04和1.72倍,LD₈₀剂量处理组3 h的GST活性与对照组无显著差异(P＞0.05),24 h后活性降低,显著低于对照组(P＜0.05)。【结论】乙基多杀菌素和联苯肼酯对地熊蜂的HQ 评估均表现为低风险,其中联苯肼酯对地熊蜂的安全性较高,在熊蜂授粉过程中可以按照推荐剂量应用,但过量施用或者长期施用可能会造成熊蜂体内药剂积累引起生理或者行为的变化,乙基多杀菌素在温室及大田授粉期的使用剂量和方法有待进一步研究。     

Reproductive success of a colony of the introduced bumblebee Bombus terrestris (L.) (Hymenoptera: Apidae) in a Tasmanian National Park

Abstract  Ever since a feral population of the bumblebee Bombus terrestris was found in suburban Hobart, on the Australian island of Tasmania, there has been ongoing debate surrounding the capacity of this species to utilise Australian native vegetation. Although several studies have reported B. terrestris foraging on Tasmanian native vegetation, doubts have been raised as to whether this reflects successful breeding in native vegetation. This study documents the success of a colony of B. terrestris in a Tasmanian National Park, isolated from urban and agricultural areas by 10 km of sea. Examination of the larval cocoons revealed that this colony had produced at least 304 new queens and 939 workers and drones. Pollen stores found in the colony were mostly from native plants, particularly Eucalyptus. These results strongly suggest that B. terrestris is able to reproduce successfully in parts of Australia that still support almost exclusively native vegetation.     

小峰熊蜂访花偏爱性

传粉昆虫在访花时,通常会表现出对某一类型花的偏爱性。本研究利用人工制作的大小、颜色、形态和气味不同的9种类型的花来研究小峰熊蜂Bombus hypocrita的访花偏爱性。结果表明：当增加花的大小、形态、气味等附加特征数时,小峰熊蜂的偏爱性程度与花朵附加特征数有显著相关性（P<0.01）。当花朵颜色由2种增加到4种,熊蜂对紫色花的偏爱性程度降低,但花朵颜色的种类与小峰熊蜂的访花偏爱性没有相关性（P>0.05）,花颜色的种类对熊蜂访紫色花的偏爱性影响不大。大小为5 cm的紫花被访次数（108±9次）明显高于大小为3 cm的紫花被访次数（40±4次）（P<0.01）,说明熊蜂明显喜欢访大花瓣的紫花。完全盛开的紫花被访次数（129±13次）显著高于刚绽放的花被访次数（26±3次）（P<0.01）,说明熊蜂喜欢访盛开的紫花。柠檬味的紫花被访次数（63±8次）明显低于草莓味的紫色花被访次数（88±2次）（P<0.05）,说明熊蜂喜欢访草莓味的花朵。     

Kin-selected conflict in the bumble-bee Bombus terrestris (Hymenoptera: Apidae)

Kin selection theory predicts conflict in social Hymenoptera between the queen and workers over male parentage because each party is more closely related to its own male offspring. Some aspects of the reproductive biology of the bumble-bee Bombus terrestris support kin selection theory but others arguably do not. We present a novel hypothesis for how conflict over male parentage should unfold in B. terrestris colonies. We propose that workers delay laying eggs until they possess information showing that egg laying suits their kin-selected interests. In colonies where queens start to lay haploid eggs early, we hypothesize that this occurs when workers detect the presence of queen-produced male brood in the brood's larval stage. In colonies where queens start to lay haploid eggs late, we hypothesize that it occurs when workers detect a signal from the queen to female larvae to commence development as queens. Our hypothesis accounts for previously unexplained aspects of the timing of reproductive events in B. terrestris, provides ultimate explanations for the results of a recent study of mechanisms underlying queen-worker conflict and helps explain this species' characteristic bimodal (split) sex ratios. Therefore, kin selection theory potentially provides a good explanation for reproductive patterns in B. terrestris.     

Does the recently introduced bumblebee Bombus terrestris (Apidae) threaten Australian ecosystems?

Abstract Native vegetation near Hobart in Tasmania was investigated to determine whether it was being invaded by the recently introduced large earth bumblebee, Bombus terrestris (Linnaeus, 1758). This species was found to be established in high numbers in a variety of vegetation types from coastal heath, through sclerophyll forest, and subalpine shrubberies up to an altitude of 1100 m. Hence, it has the potential to spread through much of Tasmania and temperate, mesic regions of mainland Australia. It is highly polylectic, foraging on at least 66 native plant species from 21 families. While the most heavily visited species produced abundant nectar, the lack of pre-dation on this species also allowed it to forage economically on small flowers in clusters. This foraging profile overlapped with those of all anthophilous insect families, all bee subgenera, and all species of nectarivorous birds which were encountered. Therefore, B. terrestris has the potential to compete with most native anthophiles and commercial honeybees. As it forages from some plant taxa which are not visited by the European honeybee, Apis mellifera Linnaeus, 1758, this species is impacting on plant-pollinator relationships which have previously been free from the effects of exotic bees.     

Nest takeover by queen and its positive impact on colony development in the Japanese bumblebee Bombus ignitus (Apidae: Hymenoptera)

Lone Bombus ignitus queens are known to start nests in small underground cavities. To examine the nest‐site preference of post‐hibernating queens, choice tests were carried out by providing queens with orphan colonies and empty cavities as possible nesting sites within an experimental box. Our results showed that the queens had a strong preference for takeover of an orphan colony, suggesting that nest takeover (usurpation) could occur in nature even with the presence of possible empty cavities for nesting. We compared the colony‐growth process and final production of sexuals between non‐takeover and takeover colonies. The increase in the number of egg cups was faster in the takeover colonies, suggesting that orphan broods elicit earlier oviposition by the usurping queen. Reproductives emerged earlier (significant for new queens) and in greater numbers (males) from takeover colonies than from non‐takeover colonies. Thus, post‐hibernating B. ignitus queens would search for and take over small orphan colonies to increase their fitness.     

Mitochondrial DNA sequence variation of the bumblebee,Bombus ardens (Hymenoptera: Apidae)

The bumblebee, Bombus ardens, is a valuable natural resource, and is most notably utilized for greenhouse pollination. In order to gain a greater understanding of the population genetic structure and the genetic diversity of this species, we sequenced a portion of the mitochondrial COI gene corresponding to the “DNA Barcode” region (658 bp) from 160 individuals collected over 15 Korean localities. Uncorrected pairwise distances among the eight haplotypes suggested low intraspecific genetic diversity, with a maximum sequence divergence of 0.3%. Such a low level of intraspecific genetic diversity was further reflected in local populations, particularly to islet populations, such as those of Youngheungdo, Jakyakdo, and Ulleugdo, which had zero genetic diversity. Geographically, one haplotype (BARBA01) was widespread and dominant, with a frequency of 90.6% (145 among 160 individuals). Other haplotypes were restricted to one to three localities and had low frequency. Overall, a very high rate of per generation female migration ratio (Nm = 4.6 to infinite) and a very low level of genetic fixation (F_ST = 0 to 0.099) were detected between pairs of localities, suggesting that the B. ardens populations on the Korean peninsula are panmictic, which is consistent with our understanding of their dispersal capability.     

Density-dependent and frequency-dependent selection by bumblebees Bombus terrestris (L.) (Hymenoptera: Apidae)

The behaviour of bumblebee workers foraging on arrays of artificial flowers of two colour morphs was observed. Experiments were conducted on arrays of varying morph frequencies and at three different total flower densities. Bumblebees consistently showed a preference for the commonest colour morph, and this behaviour was not significantly affected by changing density. In contrast, frequency-independent preferences changed significantly with density. At low densities, there was a strong bias towards the more conspicuous colour, whereas at higher densities there was no overall colour bias. Flight distances between flowers decreased significantly at high density. Bumblebees also visited flowers of similar colours sequentially, but this behaviour was not density-dependent. It is suggested that as densities increase, there is an increased probability that bumblebees detect yellow flowers, which were probably less conspicuous compared with blue flowers, and that this might be caused by changes in flight speed with flight distance. Where there is a positive relationship between pollinator visitation and the relative fitness of a floral morph, the observed behaviour would induce positive frequency-dependent selection on a plant population with two corolla colour morphs on which the bumblebees were foraging, which would result in stabilizing selection for a single corolla colour, irrespective of density. There was no indication that rare colour morphs would be preferred at high density. The probability of different corolla colour morphs going to fixation would, however, be affected by density.     

Workers dominate male production in the neotropical bumblebee Bombus wilmattae (Hymenoptera: Apidae)

Background

Cooperation and conflict in social insects are closely linked to the genetic structure of the colony. Kin selection theory predicts conflict over the production of males between the workers and the queen and between the workers themselves, depending on intra-colonial relatedness but also on other factors like colony efficiency, sex ratios, cost of worker reproduction and worker dominance behaviour. In most bumblebee (Bombus) species the queen wins this conflict and often dominates male production. However, most studies in bumblebees have been conducted with only a few selected, mostly single mated species from temperate climate regions. Here we study the genetic colony composition of the facultative polyandrous neotropical bumblebee Bombus wilmattae, to assess the outcome of the queen-worker conflict over male production and to detect potential worker policing.

Results

A total of 120 males from five colonies were genotyped with up to nine microsatellite markers to infer their parentage. Four of the five colonies were queen right at point of time of male sampling, while one had an uncertain queen status. The workers clearly dominated production of males with an average of 84.9% +/- 14.3% of males being worker sons. In the two doubly mated colonies 62.5% and 96.7% of the male offspring originated from workers and both patrilines participated in male production. Inferring the mother genotypes from the male offspring, between four to eight workers participated in the production of males.

Conclusions

In this study we show that the workers clearly win the queen-worker conflict over male production in B. wilmattae, which sets them apart from the temperate bumblebee species studied so far. Workers clearly dominated male production in the singly as well the doubly mated colonies, with up to eight workers producing male offspring in a single colony. Moreover no monopolization of reproduction by single workers occurred.     

First report of Bombus terrestris xanthopus Kriechbaumer on the Italian peninsula (Hymenoptera: Apidae)

A male specimen of Bombus terrestris (L. 1758) showing an intermediate colour between the subspecies xanthopus Kriechbaumer 1870 endemic to Corsica and the subspecies terrestris ubiquitous in the mainland was found within samples collected in 1999 on the Tuscan coast. Hybrid specimens between these subspecies are common on some of the islands of the Tuscan archipelago, while others only have pure populations. The finding is significant as it could signal the spread of the subspecies xanthopus_to the mainland. We consider and discuss the circumstances of the finding.     

Improvement of almond production using Bombus terrestris (Hymenoptera: Apidae) in Mediterranean conditions

Almond trees are one of the most important crops in the Balearic Islands. The pollination of almonds is limited to the activity of insects, and cross‐pollination is necessary for fruit development. Currently, honey bees and wild bee populations are declining considerably due to multiple causes, such as the use of pesticides, diseases and habitat loss. An alternative to increase the almond production is the use of commercial pollinators. In this long‐term (3 years) study, the effect of the introduction of Bombus terrestris colonies on almond production was evaluated in two orchards. Two experimental designs were carried out to study the best management of this pollinator. For 2 years, all bumble bee colonies were placed in the middle of the plot and during the last year, the bumble bee colonies were distributed homogenously in the plot. Fruit set and the foraging behaviour of bumble bees during the blossoming period was determined, and the effect of different environmental variables on the visitation rate of bumble bees was assessed by means of a generalized linear mixed model (GLMM). Moreover, for the first time, the spatial distribution of fruit set was evaluated. Our results show that fruit set was significantly higher in the fields where B. terrestris had been introduced than in the control plots. This increased production resulted in a positive economic balance for the farmer. Moreover, bumble bees showed to prefer trees in a southwest orientation that were close to their colony. The activity of bumble bees showed to be significantly influenced by wind speed (the higher the speed the more flowers are visited by B. terrestris) and time after flowering (visitation rate decreased with days after flowering). In order to improve its management and obtain the highest possible almond production, it is important to understand the activity and behaviour of this pollinator.     

An overview of the Bombus terrestris (L. 1758) subspecies (Hymenoptera: Apidae)

Bombus terrestris is one of the most abundant bumblebee species in the West-Palaearctic. Its widespread domestication results in the movement of many colonies. The aim of this paper is to describe the 9 subspecies currently recognised and to list some of their most obvious characteristics. Bombus terrestris is not declining anywhere, on the contrary, its synanthropic spread through domestication may be expected. However, its autumn and winter populations rely on a restricted choice of flowers so they may be threatened locally by scrub clearance and the destruction of their favourite autumnal flowers.     

Male production by non-natal workers in the bumblebee, Bombus deuteronymus (Hymenoptera: Apidae)

Social insect societies are considered to be composed of many extremely cooperative individuals. While workers are traditionally believed to behave altruistically, recent studies have revealed behaviors that are more selfish. One such example is intraspecific social parasitism, where workers invade conspecific colonies and produce male offspring that are reared by unrelated host workers. Such intraspecific parasitism has been reported in honeybees (Apis cerana, and A. florea) and “semi-wild” bumblebee colonies of Bombus terrestris. Here we report on intraspecific social parasitism by workers in “wild” colonies of the bumblebee B. deuteronymus. Three of the 11 B. deuteronymus colonies studied were invaded by non-natal workers, of which 75% became reproductive and produced 19% of the adult males. The invading non-natal workers produced significantly more males than resident natal workers and the non-natal brood was not discriminated against by the natal workers.     

Effects of clothianidin on Bombus impatiens (Hymenoptera: Apidae) colony health and foraging ability

We conducted laboratory experiments to investigate the lethal and sublethal effects of clothianidin on bumble bee, Bombus impatiens Cresson, colony health and foraging ability. Bumble bee colonies were exposed to 6 ppb clothianidin, representing the highest residue levels found in field studies on pollen, and a higher dose of 36 ppb clothianidin in pollen. Clothianidin did not effect pollen consumption, newly emerged worker weights, amount of brood or the number of workers, males, and queens at either dose. The foraging ability of worker bees tested on an artificial array of complex flowers also did not differ among treatments. These results suggest that clothianidin residues found in seed-treated canola and possibly other crops will not adversely affect the health of bumble bee colonies or the foraging ability of workers.     

Unexpected consequences of polyandry for parasitism and fitness in the bumblebee, Bombus terrestris

Multiple mating by females (polyandry) is taxonomically widespread but the evolution of such behaviors is not clearly understood given potential costs of polyandry such as time, energy, or predation risk. The genetic variability versus parasites hypothesis predicts a reduction of parasitism due to increased genetic variability among offspring and an associated fitness gain. We tested this hypothesis with a field experiment in the bumblebee, Bombus terrestris L. Worker heterogeneity within the colony was experimentally altered by artificially inseminating queens with sperm from one male, four brothers, two males, or four unrelated males. We found genetic variability to be effective, because intensity and prevalence of the most common parasite, Crithidia bombi, a trypanosome, decreased with increasing levels of colony heterogeneity. Fitness differed between treatments but did not increase in a simple way, with increasing genetic heterogeneity among colony workers. Instead, fitness followed a U-shaped function with a minimum for small amounts of genetic heterogeneity. We therefore suggest that polyandry also induces a cost, perhaps as a result of the social structure within the colony. In evolutionary terms, singly mated females appear to be constrained by an adaptive valley that needs to be crossed before high degrees of mating frequency can be reached. This may help to explain why B. terrestris and most other social insects are often monandrous.     

Extent of invasion of Tasmanian native vegetation by the exotic bumblebee Bombus terrestris (Apoidea: Apidae)

Abstract Observations of the large earth bumblebee, Bombus terrestris (L.), in native vegetation were collated to determine the extent to which this exotic species has invaded Tasmanian native vegetation during the first 9 years after its introduction. The range of B. terrestris now encompasses all of Tasmania's major vegetation types, altitudes from sea level to 1260m a.s.L, and the entire breadth of annual precipitation in the state from more than 3200 mm to less than 600 mm. Observations of workers carrying pollen, together with the presence of large numbers of bumblebees at many localities across this range indicate that colonies are frequently established in native vegetation. Evidence that colonies are often successful was obtained from repeated observations of the species during more than 1 year at particular sites. Unequivocal evidence of colonies was obtained from six National Parks, including four of the five in the Tasmanian Wilderness World Heritage Area (WHA). Indeed, the species has been present in the WHA for at least as long as it has in the city of Hobart, where it was first recorded. In southwestern Tasmania, evidence of colonies was obtained up to 40km from gardens, 61 km from small towns and 93 km from large towns. Hence, contrary to previous suggestions, the species is established in the most remote parts of Tasmania and is not dependent on introduced garden plants. Given their strong record of invasion, it is likely that B. terrestris will form feral populations on the mainland of Australia and in many other parts of the world if introduced. Because of their likely negative impacts on native animals and plants, and potential to enhance seed production in weeds, the spread of bumblebees should be avoided.     

Observations of Successful Bombus terrestris (L.) (Hymenoptera: Apidae) Colonies in Southern Tasmania

Early attempts to acclimatise Bombus spp. to Australia were not successful but a pre-1992 introduction of the bumble bee B. terrestris has succeeded and the species is slowly spreading in southern Tasmania. It is likely that the genetic base of the Tasmanian population is limited if, as is thought, only a few queens were brought from New Zealand. This may affect the rate of dispersal through the island, which presently averages 12.5 km/year. In 1995–96 18 feral colonies found in and around Hobart were transferred to nest boxes, where colony development could be monitored. All of the colonies produced queens, and the ratio of queens to workers (1:4.71) compares favourably with the upper end of colony performance scale in New Zealand (1:5.19). At least two generations are produced during warmer months and there is no indication of genetic impediments to further dispersal in Tasmania or possibly even mainland Australia. External influences such as predatory habits of birds, availability of food, competition from other insects and deliberate introduction by people into new areas make the rate of spread unpredictable.     

Genetic differentiation of continental and island populations of Bombus terrestris (Hymenoptera: Apidae) in Europe

Ten microsatellite loci and a partial sequence of the COII mitochondrial gene were used to investigate genetic differentiation in B. terrestris, a bumble bee of interest for its high-value crop pollination. The analysis included eight populations from the European continent, five from Mediterranean islands (six subspecies altogether) and one from Tenerife (initially described as a colour form of B. terrestris but recently considered as a separate species, B. canariensis). Eight of the 10 microsatellite loci displayed high levels of polymorphism in most populations. In B. terrestris populations, the total number of alleles detected per polymorphic locus ranged from 3 to 16, with observed allelic diversity from 3.8 ± 0.5 to 6.5 ± 1.4 and average calculated heterozygosities from 0.41 ± 0.09 to 0.65 ± 0.07. B. canariensis showed a significantly lower average calculated heterozygosity (0.12 ± 0.08) and observed allelic diversity (1.5 ± 0.04) as compared to both continental and island populations of B. terrestris. No significant differentiation was found among populations of B. terrestris from the European continent. In contrast, island populations were all significantly and most of them strongly differentiated from continental populations. B. terrestris mitochondrial DNA is characterized by a low nucleotide diversity: 0.18%± 0.07%, 0.20%± 0.04% and 0.27%± 0.04% for the continental populations, the island populations and all populations together, respectively. The only haplotype found in the Tenerife population differs by a single nucleotide substitution from the most common continental haplotype of B. terrestris. This situation, identical to that of Tyrrhenian islands populations and quite different from that of B. lucorum (15 substitutions between terrestris and lucorum mtDNA) casts doubts on the species status of B. canariensis. The large genetic distance between the Tenerife and B. terrestris populations estimated from microsatellite data result, most probably, from a severe bottleneck in the Canary island population. Microsatellite and mitochondrial DNA data call for the protection of the island populations of B. terrestris against importation of bumble bees of foreign origin which are used as crop pollinators.