The hypothesis that disturbance to coral reefs creates new surfaces that increase the risk of ciguatera is premised upon the increased algal substrates that develop on these surfaces being colonised by high ciguatoxin (CTX)-producing Gambierdiscus species that proliferate and enter the ciguatera food chain. Current evidence indicates that new algal substrates are indeed rapidly colonised by Gambierdiscus. However, the requirement that these Gambierdiscus species include at least one that is a significant (high) CTX-producer is more likely a limiting step. While ambient environmental conditions impact the capacity of Gambierdiscus to bloom, factors that limit the growth of the bloom could influence (typically increase) the flux of CTX entering marine food chains. Additionally, new algal substrates on damaged reefs can be preferentially grazed to funnel ciguatoxins from Gambierdiscus to herbivores in disturbed reef areas. In societies consuming second trophic level species (herbivores, grazers, and detritivores), such funnelling of CTX would increase the risk of ciguatera, although such risk would be partially offset over time by growth (toxin-dilution) and depuration. Here, we review evidence for six potential mechanisms to increase ciguatera risk from disturbance to coral reefs and suggest a hypothesis where ecosystem changes could increase the flux of CTX to groupers through a shift in predation from predominately feeding on planktonic-feeding prey to mostly feeding on benthic-feeding prey, increasing the potential for CTX to accumulate. Evidence for this hypothesis is stronger for the Pacific and Indian Oceans, and it may not apply to the Caribbean Sea/Atlantic Ocean.

We adapt previous conceptual and numerical models of ciguateric food chains for the bioaccumulation of Pacific-ciguatoxin-1 (P-CTX-1) to a general model for bioaccumulation of P-CTX3C by parrotfish (Scarus frenatus, S. niger, and S. psittacus) that feed by scraping turf algae, and surgeonfish (Naso unicornis) that mostly feed on macroalgae. We also include the Indian Ocean parrotfish Chlorurus sordidus as a model for an excavator feeding parrotfish and include comparisons with the detritivorous surgeonfish Ctenochaetus striatus that brush-feeds on turf algae. Our food chain model suggests that, of the Gambierdiscus and Fukuyoa species so far analysed for ciguatoxin (CTX) production from the Pacific, only G. polynesiensis produces sufficient P-CTX3C to consistently produce parrotfish or N. unicornis with poisonous flesh. Our model suggests that insufficient CTX would accumulate into the flesh of parrotfish or N. unicornis to become poisonous from ingesting benthic dinoflagellates producing ≤0.03 pg P-CTX3C eq./cell, except from extended feeding times on high-density blooms and in the absence of significant depuration of CTX. Apart from G. polynesiensis, only G. belizeanus and possibly G. silvae and G. australes are thought to produce >0.03 pg P-CTX3C eq./cell in the Pacific. However, with relatively low maximum concentrations of ≤0.1 pg P-CTX3C eq./cell it is likely that their contribution is minimal. Our model also suggests that the differences between the area of turf algae grazed by parrotfish and similar sized C. striatus results in greater accumulation of CTX by this surgeonfish. This makes C. striatus a higher ciguatera risk than similar sized parrotfish, either directly for human consumption or as prey for higher trophic level fishes, consistent with poisoning data from Polynesia. It also suggests the possibility that C. striatus could bioaccumulate sufficient CTX to become mildly poisonous from feeding on lower toxicity Gambierdiscus or Fukuyoa species known to produce ≥0.02 P-CTX3C eq./cell. This indicates the potential for at least two food chain pathways to produce ciguateric herbivorous fishes, depending on the CTX concentrations produced by resident Gambierdiscus or Fukuyoa on a reef and the grazing capacity of herbivorous fish. However, only G. polynesiensis appears to produce sufficient P-CTX3C to consistently accumulate in food chains to produce higher trophic level fishes that cause ciguatera in the Pacific. We incorporate CTX depuration into our model to explore scenarios where mildly poisonous parrotfish or N. unicornis ingest CTX at a rate that is balanced by depuration to estimate the Gambierdiscus/Fukuyoa densities and CTX concentrations required for these fish to remain poisonous on a reef.

We adapt previously developed conceptual and numerical models of ciguateric food chains on the Great Barrier Reef, Australia, to model the bioaccumulation of ciguatoxins (CTXs) in parrotfish, the simplest food chain with only two trophic levels. Our model indicates that relatively low (1 cell/cm2) densities of Gambierdiscus/Fukuyoa species (hereafter collectively referred to as Gambierdiscus) producing known concentrations of CTX are unlikely to be a risk of producing ciguateric fishes on the Great Barrier Reef unless CTX can accumulate and be retained in parrotfish over many months. Cell densities on turf algae equivalent to 10 Gambierdiscus/cm2 producing known maximum concentrations of Pacific-CTX-4 (0.6 pg P-CTX-4/cell) are more difficult to assess but could be a risk. This cell density may be a higher risk for parrotfish than we previously suggested for production of ciguateric groupers (third-trophic-level predators) since second-trophic-level fishes can accumulate CTX loads without the subsequent losses that occur between trophic levels. Our analysis suggests that the ratios of parrotfish length-to-area grazed and weight-to-area grazed scale differently (allometrically), where the area grazed is a proxy for the number of Gambierdiscus consumed and hence proportional to toxin accumulation. Such scaling can help explain fish size–toxicity relationships within and between trophic levels for ciguateric fishes. Our modelling reveals that CTX bioaccumulates but does not necessarily biomagnify in food chains, with the relative enrichment and depletion rates of CTX varying with fish size and/or trophic level through an interplay of local and regional food chain influences. Our numerical model for the bioaccumulation and transfer of CTX across food chains helps conceptualize the development of ciguateric fishes by comparing scenarios that reveal limiting steps in producing ciguateric fish and focuses attention on the relative contributions from each part of the food chain rather than only on single components, such as CTX production.

Invasive populations often have lower genetic diversity relative to the native-range populations from which they derive.1,2 Despite this, many biological invaders succeed in their new environments, in part due to rapid adaptation.3,4,5,6 Therefore, the role of genetic bottlenecks in constraining the adaptation of invaders is debated.7,8,9,10 Here, we use whole-genome resequencing of samples from a 10-year time-series dataset, representing the natural invasion of the Asian honey bee (Apis cerana) in Australia, to investigate natural selection occurring in the aftermath of a founding event. We find that Australia's A. cerana population was founded by as few as one colony, whose arrival was followed by a period of rapid population expansion associated with an increase of rare variants.11 The bottleneck resulted in a steep loss of overall genetic diversity, yet we nevertheless detected loci with signatures of positive selection during the first years post-invasion. When we investigated the origin of alleles under selection, we found that selection acted primarily on the variation introduced by founders and not on the variants that arose post-invasion by mutation. In all, our data highlight that selection on standing genetic variation can occur in the early years post-invasion, even where founding bottlenecks are severe.

Published data were used to model the transfer of ciguatoxins (CTX) across three trophic levels of a marine food chain on the Great Barrier Reef (GBR), Australia, to produce a mildly toxic common coral trout (Plectropomus leopardus), one of the most targeted food fishes on the GBR. Our model generated a 1.6 kg grouper with a flesh concentration of 0.1 µg/kg of Pacific-ciguatoxin-1 (P-CTX-1 = CTX1B) from 1.1 to 4.3 µg of P-CTX-1 equivalents (eq.) entering the food chain from 0.7 to 2.7 million benthic dinoflagellates (Gambierdiscus sp.) producing 1.6 pg/cell of the P-CTX-1 precursor, P-CTX-4B (CTX4B). We simulated the food chain transfer of ciguatoxins via surgeonfishes by modelling Ctenochaetus striatus feeding on turf algae. A C. striatus feeding on ≥1000 Gambierdiscus/cm2 of turf algae accumulates sufficient toxin in <2 days that when preyed on, produces a 1.6 kg common coral trout with a flesh concentration of 0.1 µg/kg P-CTX-1. Our model shows that even transient blooms of highly ciguatoxic Gambierdiscus can generate ciguateric fishes. In contrast, sparse cell densities of ≤10 Gambierdiscus/cm2 are unlikely to pose a significant risk, at least in areas where the P-CTX-1 family of ciguatoxins predominate. The ciguatera risk from intermediate Gambierdiscus densities (~100 cells/cm2) is more difficult to assess, as it requires feeding times for surgeonfish (~4–14 days) that overlap with turnover rates of turf algae that are grazed by herbivorous fishes, at least in regions such as the GBR, where stocks of herbivorous fishes are not impacted by fishing. We use our model to explore how the duration of ciguatoxic Gambierdiscus blooms, the type of ciguatoxins they produce, and fish feeding behaviours can produce differences in relative toxicities between trophic levels. Our simple model indicates thresholds for the design of risk and mitigation strategies for ciguatera and the variables that can be manipulated to explore alternate scenarios for the accumulation and transfer of P-CTX-1 analogues through marine food chains and, potentially, for other ciguatoxins in other regions, as more data become available.

Cells in a clonal culture of the WC1/1 strain of Gambierdiscus that produced ciguatoxin and maitotoxin-3 were observed to spontaneously fuse during the light phase of culture growth. Cells in the process of fusion were indistinguishable from other cells under the light microscope, except that at least one (often both) of the fusing cells displayed an extendible, finger-like protrusion (presumed peduncle) arising from near the sulcul region. Fusion started with one of the cells turning 90° to place the planes of the girdles approximately at right angles to each other, and movement of the transverse flagella ceased in both cells, or in the cell seen in girdle (lateral) view. The cell in girdle view appeared to fuse into the theca of the other cell. The cell that had turned 90° often rounded up and become egg shaped (obovoid) during early fusion. Fusion can be quick (<10 min) or can take more than an hour. We saw no evidence of the theca being shed during fusion. Measurement of the dorsoventral and transdiameters revealed a wide range for cell sizes that were distributed as a bimodal population in the clonal culture. This bimodal cell population structure was maintained in clonal cultures reisolated from a small or large cell from the original WC1/1 culture. Cellular production of ciguatoxins by the WC1/1 clone increased during the first two years in culture with a corresponding decrease in production of maitotoxin-3, but this inverse relationship was not maintained over the following ~1.5 years.

To begin to understand the impact of food chain dynamics on ciguatera risk, we used published data to model the transfer of ciguatoxins across four trophic levels of a marine food chain in Platypus Bay, Australia. The data to support this first attempt to conceptualize the scale of each trophic transfer step was limited, resulting in broad estimates. The hypothetical scenario we explored generated a low-toxicity 10 kg Spanish mackerel (Scomberomorus commerson) with a flesh concentration of 0.1 µg/kg of Pacific-ciguatoxin-1 (P-CTX-1, also known as CTX1B) from 19.5–78.1 µg of P-CTX-1 equivalents (eq.) that enter the marine food chain from a population of 12–49 million benthic dinoflagellates (Gambierdiscus sp.) producing 1.6 × 10−12 g/cell of the P-CTX-1 precursor, P-CTX-4B. This number of Gambierdiscus could be epiphytic on 22–88 kg of the benthic macroalgae (Cladophora) that carpets the bottom of much of Platypus Bay, with the toxin transferred to an estimated 40,000–160,000 alpheid shrimps in the second trophic level. This large number of shrimps appears unrealistic, but toxic shrimps would likely be consumed by a school of small, blotched javelin fish (Pomadasys maculatus) at the third trophic level, reducing the number of shrimps consumed by each fish. The Spanish mackerel would accumulate a flesh concentration of 0.1 µg/kg P-CTX-1 eq. by preying upon the school of blotched javelin and consuming 3.6–14.4 µg of P-CTX-1 eq. However, published data indicate this burden of toxin could be accumulated by a 10 kg Spanish mackerel from as few as one to three blotched javelin fish, suggesting that much greater amounts of toxin than modelled here must at certain times be produced and transferred through Platypus Bay food chains. This modelling highlights the need for better quantitative estimates of ciguatoxin production, biotransformation, and depuration through marine food chains to improve our understanding and management of ciguatera risk.

Introduced species are a significant global concern because they can disrupt native ecosystems and cause economic damage to agricultural systems and infrastructure. The mitochondrial DNA (mtDNA) diversity of invasive populations can help to identify the source and number of incursions and reveal whether these populations have maintained standing genetic variation that might allow mitochondrial genomes to adapt to new environments. We investigated mitochondrial diversity in native and invasive populations of the Asian honey bee ( Apis cerana ). We generated 144 sequences of mitochondrial cytochrome c oxidase subunit I (COI) from samples spanning three invasive populations (Australia, New Guinea and Solomon Islands) and three native‐range Indonesian populations (Java, Sulawesi and Flores). We then analysed these sequences together with published COI sequences to evaluate changes in mtDNA diversity associated with the recent spread of A. cerana across the Austral‐Pacific region. Mitochondrial COI diversity was consistent with invasive A. cerana populations having endured severe founder event bottlenecks during colonisation of New Guinea from Java, and then again during colonisation of Australia and the Solomon Islands from New Guinea. Mitochondrial diversity of native‐range Indonesian populations was high (26 COI haplotypes detected), particularly on Java (20 haplotypes), while all samples from invasive populations carried the same COI haplotype. Indeed, the single COI haplotype of invasive A. cerana populations is consistent with invasive populations being founded by just one, or very few, queens, as previously suggested from nuclear markers. Further investigation is needed to understand the fitness effects, if any, of mitochondrial diversity loss in invasive A. cerana populations of the Austral‐Pacific.

Male honey bees trapped at Drone Congregation Areas (DCAs) can be used to infer the number of colonies from which drones were derived, and thereby colony density in the environment. Crucial to the accuracy of this method is precise grouping of males into brother groups based on genetic markers, and a sample size that is sufficient so that all colonies in the area are included in the sample. The optimal sample size is a trade-off between cost and accuracy and cannot be known prior to sampling. Therefore, follow-up surveys may be necessary if the data indicate that the first sample was too small. However, the effect of multiple sampling on allele frequency estimates and the accuracy of the method is poorly understood. Here we trapped drones from two independent DCAs every month over 2 and 2.5 years. We analysed our data using the sibship grouping programme COLONY in three ways: (i) using data from the entire year, and counting the number of colonies identified in each month; (ii) using monthly data with allele frequencies from the entire season; and (iii) using data from each month separately. Although there were significant changes in allele frequencies over the year, these changes had no material effect on classifications of drones into families. Therefore, multiple samples can provide more robust estimates of family groupings due to the larger sample size and can be used with confidence where required.

The ability to clone oneself has clear benefits-no need for mate hunting or dilution of one's genome in offspring. It is therefore unsurprising that some populations of haplo-diploid social insects have evolved thelytokous parthenogenesis-the virgin birth of a female. But thelytokous parthenogenesis has a downside: the loss of heterozygosity (LoH) as a consequence of genetic recombination. LoH in haplo-diploid insects can be highly deleterious because female sex determination often relies on heterozygosity at sex-determining loci. The two female castes of the Cape honeybee, Apis mellifera capensis, differ in their mode of reproduction. While workers always reproduce thelytokously, queens always mate and reproduce sexually. For workers, it is important to reduce the frequency of recombination so as to not produce offspring that are homozygous. Here, we ask whether recombination rates differ between Cape workers and Cape queens that we experimentally manipulated to reproduce thelytokously. We tested our hypothesis that Cape workers have evolved mechanisms that restrain genetic recombination, whereas queens have no need for such mechanisms because they reproduce sexually. Using a combination of microsatellite genotyping and whole-genome sequencing we find that a reduction in recombination is confined to workers only.

We review and develop conceptual models for the bio-transfer of ciguatoxins in food chains for Platypus Bay and the Great Barrier Reef on the east coast of Australia. Platypus Bay is unique in repeatedly producing ciguateric fishes in Australia, with ciguatoxins produced by benthic dinoflagellates (Gambierdiscus spp.) growing epiphytically on free-living, benthic macroalgae. The Gambierdiscus are consumed by invertebrates living within the macroalgae, which are preyed upon by small carnivorous fishes, which are then preyed upon by Spanish mackerel (Scomberomorus commerson). We hypothesise that Gambierdiscus and/or Fukuyoa species growing on turf algae are the main source of ciguatoxins entering marine food chains to cause ciguatera on the Great Barrier Reef. The abundance of surgeonfish that feed on turf algae may act as a feedback mechanism controlling the flow of ciguatoxins through this marine food chain. If this hypothesis is broadly applicable, then a reduction in herbivory from overharvesting of herbivores could lead to increases in ciguatera by concentrating ciguatoxins through the remaining, smaller population of herbivores. Modelling the dilution of ciguatoxins by somatic growth in Spanish mackerel and coral trout (Plectropomus leopardus) revealed that growth could not significantly reduce the toxicity of fish flesh, except in young fast-growing fishes or legal-sized fishes contaminated with low levels of ciguatoxins. If Spanish mackerel along the east coast of Australia can depurate ciguatoxins, it is most likely with a half-life of ≤1-year. Our review and conceptual models can aid management and research of ciguatera in Australia, and globally.

It is often necessary to assess the density of honey bee colonies in an environment. In theory, a random sample of males obtained at a mating lek (Drone Congregation Area) can be used to infer the number of queens that contributed sons to the sample, and thereby estimate colony density based on the area from which drones are drawn to a DCA. Because of its utility and efficiency, the technique is being increasingly used. However, the accuracy of the method has never been evaluated, and there are no recommendations for sample size. Here, we infer the genotypes of 322 mother queens from the genotypes of 2329 drones caught at a single DCA using the program COLONY. We then use this realistic pool of queen genotypes to generate multiple simulated data sets of drone genotypes, varying the number of queens and sons that each queen contributed to the sample. We find that the technique provides an accurate estimate (<10% error) of the total number of families present in a drone sample, provided that queens contribute at least six drones to the sample on average. This threshold can be reduced when colony density is low. Non‐sampling error only becomes significant when queens contribute fewer than three sons on average across simulated samples. We conclude that the technique is robust and can be used with confidence provided that the sample size is adequate.

Reliable information on Western honey bee colony density can be important in a variety of contexts including biosecurity responses, determining the sufficiency of pollinators in an agroecosystem and in determining the impacts of feral honey bees on ecosystems. Indirect methods for estimating colony density based on genetic analysis of sampled males are more feasible and cost efficient than direct observation in the field. Microsatellite genotypes of drones caught using Williams drone trap are used to identify the number of colonies (queens) that contributed drones to a mating lek. From the number of colonies, the density of colonies can be estimated based on assumptions about the area from which drones are drawn. This requires reliable estimates of drone flight distance. We estimated average minimum flight distance of drones from feral colonies along two 7-km transects in Southern NSW, Australia. We found that drones from feral colonies flew at least 3.5 km to drone traps. We then determined that the maximum distance that drones flew from a focal colony to a trap was 3.75 km. We conclude that a drone trap samples an area of 44 km 2 , and that this area should be used to convert estimated colony numbers to colony densities. This area is much greater than has been previously assumed. The densities of honey bee colonies in Grong Grong and Currawarna, NSW, are 1.38–2.73 and 1.31–3.06 colonies/km 2 respectively.

Honey bee workers can lay eggs that result in viable males (drones). In queenless colonies, workers activate their ovaries and lay eggs, both in their own colony and in other queenless colonies. While worker reproduction and reproductive parasitism are well demonstrated, the direct contribution of reproductive workers to the gene pool is unclear. Queenless workers mostly lay their eggs in worker-sized brood cells. The resulting drones are smaller than normal drones. We determined two measures of forewing size in drones reared in drone-sized cells (DC) and in worker-sized cells (WC). Forewing length and width were 5.78 ± 0.26 mm (± SD) and 1.27 ± 0.08 mm, respectively, for drones reared in DC, and 5.01 ± 0.21 mm and 1.11 ± 0.05 mm for drones reared in WC. Discriminant function analysis indicated that forewing length alone is sufficient to differentiate DC and WC drones. To determine the contribution of worker-laid drones to the mating population, we sampled males at a natural mating lek using a Williams’ drone trap every month for 12 months. We used the discriminant function to assign drones as being DC or WC based on their forewing length and a strict classification criterion of ≥ 0.99% posterior probability of assignment to one or other group. We estimate that about 0.23% of sampled males were reared in WC and were, therefore, likely to have been laid by workers. Our results suggest that queenless workers and queenless colonies make a small contribution to the male mating population, and that this contribution may be sufficient to provide ongoing selection for worker reproductive parasitism.

Transportation networks play a crucial role in human and animal societies. For a transportation network to be efficient, it must have adequate capacity to meet traffic demand. Network design becomes increasingly difficult in situations where traffic demand can change unexpectedly. In humans, network design is often constrained by path dependency because it is difficult to move a road once it is built. A similar issue theoretically faces pheromone-trail-laying social insects; once a trail has been laid, positive feedback makes re-routing difficult because new trails cannot compete with continually reinforced pre-existing trails. In the present study, we examined the response of Argentine ant colonies and their trail networks to variable environments where resources differ in quality and change unexpectedly. We found that Argentine ant colonies effectively tracked changes in food quality such that colonies allocated the highest proportion of foragers to the most rewarding feeder. Ant colonies maximised access to high concentration feeders by building additional trails and routes connecting the nest to the feeder. Trail networks appeared to form via a pruning process in which lower traffic trails were gradually removed from the network. At the same time, we observed several instances where new trails appear to have been built to accommodate a surge in demand. The combination of trail building when traffic demand is high and trail pruning when traffic demand is low results in a demand-driven network formation system that allows ants to monopolise multiple dynamic resources.

The notion that honeybee colonies are harmonious, isolated societies in which workers selflessly sacrifice their reproductive opportunities to serve their queen has long been debunked. Like any society, honeybee colonies contain selfish individuals that pursue their own interests, or cheat, at the expense of the colony, and these individuals need to be controlled. There are numerous studies detailing the myriad ways in which selfish workers may subvert the typical dominance hierarchy of a haplo-diploid insect society. Recent studies have focussed on thelytoky, the ability to produce diploid offspring without mating, as the most significant attribute of a successful reproductive parasite. However, we argue that thelytoky is not necessary for successful parasitism, and that even arrhenotokous societies contain specialized reproductive parasites. Using A. mellifera and A. cerana as examples, we show that the most important aspects of a would-be reproductive cheat’s success are an ability to escape policing and the timing of the reproductive attempt. Finally, we show that thelytoky, while not necessary for the evolution of successful reproductive parasites, can give rise to specialized parasitic lineages and that such lineages are likely to be far more common than previously assumed.

Most societies are vulnerable to rogue individuals that pursue their own interests at the expense of the collective entity. Societies often protect themselves from selfish behaviour by ‘policing’, thereby enforcing the interests of the collective over those of individuals. In insect societies, for example, selfish workers can activate their ovaries and lay eggs, exploiting the collective brood rearing system for individual benefit. Policing, usually in the form of oophagy of worker‐laid eggs, controls selfish behaviour. Importantly, once an effective system of policing has evolved, the incentive for personal reproduction is lost, and ‘reproductive acquiescence’ in which ovary activation is rare or absent is predicted to evolve. Studies of social Hymenoptera have largely supported the prediction of worker ‘acquiescence’; workers of most species where policing is well developed have inactive ovaries. However, the eastern honeybee Apis cerana appears to be an exception. A. cerana colonies are characterized by highly efficient policing, yet about 5% of workers have active ovaries, even when a queen is present. This suggests that the evolution of acquiescence is incomplete in A. cerana . We regularly sampled male eggs and pupae from four A. cerana colonies. Workers had high levels of ovary activation overall (11.7%), and 3.8% of assignable male eggs and 1.1% of assignable male pupae were worker‐laid. We conclude that workers with active ovaries lay their eggs, but these rarely survive to pupation because of intense policing. We then used our findings as well as previously published data on A. cerana and A. mellifera to redo the meta‐analysis on which reproductive acquiescence theory is based. Including data on both species did not affect the relationship between effectiveness of policing and levels of worker reproduction. Their inclusion did, however, seriously weaken the relationship between relatedness among workers and levels of worker reproduction. Our work thus suggests that relatedness among workers does not affect the probability that workers will attempt to reproduce, but that it is coercion by peers that limits worker reproduction.

Dinoflagellates are microscopic, mostly unicellular algae that live in freshwater and marine waters. Only a relatively small number of Dinoflagellate species produce bioactive molecules that are toxic to other organisms. This chapter discusses the marine dinoflagellates known to produce toxins, especially those species that produce toxins that accumulate through food chains to cause human poisoning. In addition to dinoflagellates, a number of freshwater and brackish species of cyanobacteria are known to produce the toxins. The majority of paralytic Shellfish poisoning contamination of Shellfish around the world is caused by species of the planktonic Dinoflagellate belonging to the genus Alexandrium. Neurotoxic Shellfish poisoning is a neurological disease caused by eating Shellfish contaminated with lipid-soluble, polyether toxins called brevetoxins. Gambierdiscus spp. are benthic dinoflagellates that are mostly found as epiphytes in oligotrophic waters on a range of biotic and abiotic substrates including macroalgae, turf algae, detritus, and sand.

Honeybee workers generally refrain from personal reproduction when a queen is present. Workers discern the presence and fecundity of the queen via volatile pheromones that permeate throughout the colony. Pheromones are emitted both by the queen herself and by the brood that she produces. If pheromone production is disrupted, some workers initiate egg laying. The Eastern honeybee Apis cerana is unusual in that workers have high levels of ovary activation even in the presence of a queen. To investigate the effect of disruption to pheromone dispersal, we fitted three A. cerana colonies with vertical queen excluders, thus splitting the colonies into a half containing a queen and a half without a queen. We regularly sampled adult workers from both sides of the excluder for 3 weeks. We also sampled workers from three control colonies that did not contain excluders. We found a significant increase in worker ovary activation 3 days after addition of excluders, suggesting that the reduced dispersal of pheromones allowed some workers to become reproductively active. Workers attempted to rear queen cells on the queenless halves of all three colonies. Queen-rearing ceased on day 9, at which time no queen-laid brood remained on the queenless halves of the colonies. Ovary activation rates continued to climb until day 9 and then gradually began to decline. With the exception of one egg, we did not observe worker-laid brood on the queenless side of the colonies, suggesting that workers continued policing eggs laid by workers. We conclude that if the distribution of brood pheromone is impeded, workers prepare to supersede their queen, accompanied by high levels of worker ovary activation. However, because workers continue to police each other, high ovary activation does not result in worker-produced drones.