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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 km2, 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/km2 respectively. [ABSTRACT FROM AUTHOR]

We examine the origin of honey bee (Apis mellifera) populations in Kangaroo Island (Australia), Norfolk Island (Australia) and the Kingdom of Tonga using a highly polymorphic mitochondrial DNA region and a panel of 37 single nucleotide polymorphisms that assigns ancestry to three evolutionary lineages: Eastern Europe, Western Europe and Africa. We also examine inbreeding coefficients and genetic variation using microsatellites and mitochondrial sequencing. The honey bees of Kangaroo Island have a high proportion of Eastern European ancestry (90.2%), consistent with claims that they are of the subspecies A. m. ligustica. The honey bees of Norfolk Island also had a majority of ancestry from Eastern Europe (73.1%) with some contribution from Western Europe (21.2%). The honey bees of Tonga are mainly of Western European (70.3%) origin with some Eastern European ancestry (27.4%). Despite the suspected severe bottlenecks experienced by these island population, inbreeding coefficients were low. [ABSTRACT FROM AUTHOR]

Inbreeding (the mating between closely related individuals) often has detrimental effects that are associated with loss of heterozygosity at overdominant loci, and the expression of deleterious recessive alleles. However, determining which loci are detrimental when homozygous, and the extent of their phenotypic effects, remains poorly understood. Here, we utilize a unique inbred population of clonal (thelytokous) honey bees, Apis mellifera capensis, to determine which loci reduce individual fitness when homozygous. This asexual population arose from a single worker ancestor approximately 20 years ago and has persisted for at least 100 generations. Thelytokous parthenogenesis results in a 1/3 of loss of heterozygosity with each generation. Yet, this population retains heterozygosity throughout its genome due to selection against homozygotes. Deep sequencing of one bee from each of the three known sub‐lineages of the population revealed that 3,766 of 10,884 genes (34%) have retained heterozygosity across all sub‐lineages, suggesting that these genes have heterozygote advantage. The maintenance of heterozygosity in the same genes and genomic regions in all three sub‐lineages suggests that nearly every chromosome carries genes that show sufficient heterozygote advantage to be selectively detrimental when homozygous. [ABSTRACT FROM AUTHOR]

Functional worker sterility is the defining feature of insect societies. Yet, workers are sometimes found reproducing in their own or foreign colonies. The proximate mechanisms underlying these alternative reproductive phenotypes are keys to understanding how reproductive altruism and selfishness are balanced in eusocial insects. In this study, we show that in honeybee ( Apis mellifera) colonies, the social environment of a worker, that is, the presence and relatedness of the queens in a worker's natal colony and in surrounding colonies, significantly influences her fertility and drifting behaviour. Furthermore, subfamilies vary in the frequency of worker ovarian activation, propensity to drift and the kind of host colony that is targeted for reproductive parasitism. Our results show that there is an interplay between a worker's subfamily, reproductive state and social environment that substantially affects her reproductive phenotype. Our study further indicates that honeybee populations show substantial genetic variance for worker reproductive strategies, suggesting that no one strategy is optimal under all the circumstances that a typical worker may encounter. [ABSTRACT FROM AUTHOR]

Epigenetic modifications, mediated by DNA methylation, are involved in caste differentiation between queen and worker honey bees, Apis mellifera. This study uses methylation sensitive amplified fragment length polymorphism (MS-AFLP) to investigate whether genome-wide DNA methylation is implicated in the regulation of honey bee worker sterility and whether CO2 narcosis, which suppresses ovary activation in queenless workers, influences DNA methylation. Queenless workers were divided into control and experimental (CO2 narcosis) cages. We compared MS-AFLP patterns in CO2-treated and non-treated workers with and without activated ovaries at 4 h, 2 and 7 days after treatment. While there was evidence of DNA methylation in all samples, there was no detectable difference in genome-wide methylation patterns between any treatment comparisons. This suggests that mechanisms that regulate worker sterility in the adult honey bee worker are not related to genome-wide methylation, and that CO2 narcosis does not significantly affect DNA methylation patterns in the worker ovary. However, because DNA methylation is sparse in the honey bee, and because MS-AFLP detects only a proportion of methylated sites, it remains possible that a subset of genes that are responsible for the regulation of worker sterility are differentially methylated, but that we failed to pick these up in our genome-wide scan. [ABSTRACT FROM AUTHOR]

When a honeybee ( Apis spp.) colony loses its queen and is unable to rear a new one, some of the workers activate their ovaries and produce eggs. When a colony has a queen (i.e., it is queenright) almost all worker-laid eggs are eaten, but when hopelessly queenless, the workers become more tolerant of worker-laid eggs and rear some of them to adult drones. This increased tolerance renders a queenless colony vulnerable to worker reproductive parasitism, wherein unrelated workers enter the colony and lay eggs. Here, we show that the proportion of unrelated (non-natal) workers significantly decreases after an Apis mellifera colony becomes queenless. The remaining non-natal workers are as likely to have activated ovaries as natal workers, yet they produce more eggs than natal workers, resulting in significantly higher reproductive success for non-natal workers. In a second experiment, we provided queenless and queenright workers with a choice to remain in their own colony or to join a queenless or queenright colony nearby. The experiment was set up such that worker movement was unlikely to be due to simple orientation errors. Very few workers joined another colony, and there was no preference for workers to drift into or out of queenless or queenright colonies, in accordance with the proportion of non-natal workers declining significantly after becoming queenless in the first experiment. [ABSTRACT FROM AUTHOR]

Due to the introduction of exotic honey bee (Apis mellifera L.) diseases in the eastern states, the borders of the state of Western Australia were closed to the import of bees for breeding and other purposes >25 yr ago. To provide genetically improved stock for the industry, a closed population breeding program was established that now provides stock for the majority of Western Australian beekeepers. Given concerns that inbreeding may have resulted from the closed population breeding structure, we assessed the genetic diversity within and between the breeding lines by using microsatellite and mitochondrial markers. We found that the breeding population still maintains considerable genetic diversity, despite 25 yr of selective breeding. We also investigated the genetic distance of the closed population breeding program to that of beekeepers outside of the program, and the feral Western Australian honey bee population. The feral population is genetically distinct from the closed population, but not from the genetic stock maintained by beekeepers outside of the program. The honey bees of Western Australia show three mitotypes, originating from two subspecies: Apis mellifera ligustica (mitotypes C1 and M7b) and Apis mellifera iberica (mitotype M6). Only mitotypes C1 and M6 are present in the commercial populations. The feral population contains all three mitotypes. [ABSTRACT FROM AUTHOR]

The queen of a honeybee colony has a reproductive monopoly because her workers' ovaries are normally inactive and any eggs that they do lay are eaten by their fellow workers. But if a colony becomes queenless, the workers start to lay eggs, stop policing and rear a last batch of males before the colony finally dies out. Here we show that workers of the Asian dwarf red honeybee Apis florea from other colonies exploit this interval as an opportunity to move in and lay their own eggs while no policing is in force. Such parasitism of queenless colonies does not occur in the western honeybee A. mellifera and may be facilitated by the accessibility of A. florea nests, which are built out in the open. [ABSTRACT FROM AUTHOR]