ORCID Profile
0000-0002-9040-3756
Current Organisation
University of Sydney
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Publisher: Springer Science and Business Media LLC
Date: 23-03-2011
DOI: 10.1038/NATURE09832
Abstract: Arising from M. A. Nowak, C. E. Tarnita & E. O. Wilson 466, 1057-1062 (2010) Nowak et al. reply. The paper by Nowak et al. has the evolution of eusociality as its title, but it is mostly about something else. It argues against inclusive fitness theory and offers an alternative modelling approach that is claimed to be more fundamental and general, but which, we believe, has no practical biological meaning for the evolution of eusociality. Nowak et al. overlook the robust empirical observation that eusociality has only arisen in clades where mothers are associated with their full-sibling offspring that is, in families where the average relatedness of offspring to siblings is as high as to their own offspring, independent of population structure or ploidy. We believe that this omission makes the paper largely irrelevant for understanding the evolution of eusociality.
Publisher: Springer Science and Business Media LLC
Date: 03-01-2015
Publisher: The Royal Society
Date: 22-08-1998
Publisher: Springer Science and Business Media LLC
Date: 09-04-2011
Publisher: Wiley
Date: 05-11-2011
DOI: 10.1111/J.1558-5646.2010.01164.X
Abstract: The honey bee population of South Africa is ided into two subspecies: a northern population in which queenless workers reproduce arrhenotokously and a southern one in which workers reproduce thelytokously. A hybrid zone separates the two, but on at least three occasions the northern population has become infested by reproductive workers derived from the southern population. These parasitic workers lay in host colonies parthenogenetically, resulting in yet more parasites. The current infestation is 20-year old--surprising because an asexual lineage is expected to show a decline in vigor over time due to increasing homozygosity. The decline is expected to be acute in honey bees, where homozygosity at the sex locus is lethal. We surveyed colonies from the zone of infestation and genotyped putative parasites at two sets of linked microsatellite loci. We confirm that there is a single clonal lineage of parasites that shows minor variations arising from recombination events. The lineage shows high levels of heterozygosity, which may be maintained by selection against homozygotes, or by a reduction in recombination frequency within the lineage. We suggest that the clonal lineage can endure the costs of asexual reproduction because of the fitness benefits of its parasitic life history.
Publisher: Springer Science and Business Media LLC
Date: 28-07-2005
DOI: 10.1007/S00359-005-0034-0
Abstract: Honey bee foragers communicate the direction and distance of both food sources and new nest sites to nest mates by means of a symbolic dance language. Interestingly, the precision by which dancers transfer directional information is negatively correlated with the distance to the advertised food source. The 'tuned-error' hypothesis suggests that colonies benefit from this imprecision as it spreads recruits out over a patch of constant size irrespective of the distance to the advertised site. An alternative to the tuned-error hypothesis is that dancers are physically incapable of dancing with great precision for nearby sources. Here we revisit the tuned-error hypothesis by studying the change in dance precision with increasing foraging distance over relatively short distances while controlling for environmental influences. We show that bees indeed increase their dance precision with the increase in foraging distance. However, we also show that dance performed by swarm-scouts for a nearby (30 m) nest site, where there could be no benefit to imprecision, are either without or with only limited directional information. This result suggests that imprecision in dance communication is caused primarily by physical constraints in the ability of dancers to turn around quickly enough when the advertised site is nearby.
Publisher: Wiley
Date: 09-2023
DOI: 10.1002/ECE3.10508
Publisher: Springer Science and Business Media LLC
Date: 30-04-2015
Publisher: Springer Science and Business Media LLC
Date: 08-10-2018
Publisher: The Royal Society
Date: 08-09-2010
Abstract: Speed–accuracy trade-offs (SATs) are thought to be a fundamental feature of biological information processing, yet most evidence of SATs comes from animals. Here, we examine SATs in the foraging decisions of an acellular, amoeboid organism: the slime mould Physarum polycephalum . Slime moulds were given a simple discrimination task: selecting the highest-quality food item from a set of three options. We investigated the effect of two stressors, light exposure and hunger, on the speed and accuracy of decision-making. We also examined the effect of task difficulty. When given a difficult discrimination task, stressed in iduals tend to make faster decisions than non-stressed in iduals. This effect was reversed in plasmodia given easy discrimination tasks, where stressed in iduals made slower decisions than non-stressed in iduals. We found evidence of SATs, such that in iduals who made fast decisions were more likely to make costly errors by selecting the worst possible food option. Our results suggest that SATs occur in a wider range of taxa than previously considered.
Publisher: The Company of Biologists
Date: 15-02-2017
DOI: 10.1242/JEB.144238
Abstract: 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.
Publisher: Wiley
Date: 07-2019
DOI: 10.1111/BRV.12542
Abstract: The question 'what is an in idual' does not often arise in studies within the field of behavioural ecology. Generally behavioural ecologists do not think about what makes an in idual because they tend to use intuitive working concepts of in iduality. Rarely do they explicitly mention how in iduality affects their experimental design and interpretation of results. By contrast, the concept of in iduality continues to intrigue philosophers of biology. It is interesting that while philosophers of biology debate definitions of in iduality, biologists generally use the concept of in iduality every day without much thought. Here we review the philosophical approaches to defining biological in iduality, and illustrate how the biological in iduality concepts used by biologists are affected by their study question and choice of organism. We clarify the behavioural perspective of biological in iduality by introducing the concept of the behavioural in idual. The notion of the behavioural in idual is particularly interesting when explored in less-conventional study organisms. By including less-conventional organisms, it becomes clear why the concept of biological in iduality is usually intuitive in behavioural ecology.
Publisher: Informa UK Limited
Date: 2000
Publisher: Oxford University Press (OUP)
Date: 05-2017
Publisher: Springer Berlin Heidelberg
Date: 2008
Publisher: Proceedings of the National Academy of Sciences
Date: 09-03-2010
Abstract: A fundamental question in nutritional biology is how distributed systems maintain an optimal supply of multiple nutrients essential for life and reproduction. In the case of animals, the nutritional requirements of the cells within the body are coordinated by the brain in neural and chemical dialogue with sensory systems and peripheral organs. At the level of an insect society, the requirements for the entire colony are met by the foraging efforts of a minority of workers responding to cues emanating from the brood. Both ex les involve components specialized to deal with nutrient supply and demand (brains and peripheral organs, foragers and brood). However, some of the most species-rich, largest, and ecologically significant heterotrophic organisms on earth, such as the vast mycelial networks of fungi, comprise distributed networks without specialized centers: How do these organisms coordinate the search for multiple nutrients? We address this question in the acellular slime mold Physarum polycephalum and show that this extraordinary organism can make complex nutritional decisions, despite lacking a coordination center and comprising only a single vast multinucleate cell. We show that a single slime mold is able to grow to contact patches of different nutrient quality in the precise proportions necessary to compose an optimal diet. That such organisms have the capacity to maintain the balance of carbon- and nitrogen-based nutrients by selective foraging has considerable implications not only for our understanding of nutrient balancing in distributed systems but for the functional ecology of soils, nutrient cycling, and carbon sequestration.
Publisher: Springer Science and Business Media LLC
Date: 15-08-2007
Publisher: Oxford University Press (OUP)
Date: 06-12-2008
Publisher: Wiley
Date: 02-02-2012
DOI: 10.1111/J.1558-5646.2011.01543.X
Abstract: An asexual lineage that reproduces by automictic thelytokous parthenogenesis has a problem: rapid loss of heterozygosity resulting in effective inbreeding. Thus, the circumstances under which rare asexual lineages thrive provide insights into the trade-offs that shape the evolution of alternative reproductive strategies across taxa. A socially parasitic lineage of the Cape honey bee, Apis mellifera capensis, provides an ex le of a thelytokous lineage that has endured for over two decades. It has been proposed that cytological adaptations slow the loss of heterozygosity in this lineage. However, we show that heterozygosity at the complementary sex determining (csd) locus is maintained via selection against homozygous diploid males that arise from recombination. Further, because zygosity is correlated across the genome, it appears that selection against diploid males reduces loss of homozygosity at other loci. Selection against homozygotes at csd results in substantial genetic load, so that if a thelytokous lineage is to endure, unusual ecological circumstances must exist in which asexuality permits such a high degree of fecundity that the genetic load can be tolerated. Without these ecological circumstances, sex will triumph over asexuality. In A. m. capensis, these conditions are provided by the parasitic interaction with its conspecific host, Apis mellifera scutellata.
Publisher: Springer Science and Business Media LLC
Date: 27-10-2010
Publisher: Springer Science and Business Media LLC
Date: 12-09-2008
Abstract: Hybrid zones are found wherever two populations distinguishable on the basis of heritable characters overlap spatially and temporally and hybridization occurs. If hybrids have lower fitness than the parental types a tension zone may emerge, in which there is a barrier to gene flow between the two parental populations. Here we discuss a hybrid zone between two honeybee subspecies, Apis mellifera capensis and A. m. scutellata and argue that this zone is an ex le of a tension zone. This tension zone is particularly interesting because A. m. capensis can be a lethal social parasite of A. m. scutellata. However, despite its parasitic potential, A. m. capensis appears to be unable to increase its natural range unassisted. We propose three interlinked mechanisms that could maintain the South African honeybee hybrid zone: (1) low fitness of intercrossed and genetically mixed colonies arising from inadequate regulation of worker reproduction (2) higher reproductive success of A. m. scutellata via both high dispersal rates into the hybrid zone and increased competitiveness of males, countered by (3) the parasitic nature of A. m. capensis.
Publisher: Oxford University Press (OUP)
Date: 2009
Publisher: Elsevier BV
Date: 08-2005
Publisher: American Association for the Advancement of Science (AAAS)
Date: 30-05-2008
Abstract: Close relatedness has long been considered crucial to the evolution of eusociality. However, it has recently been suggested that close relatedness may be a consequence, rather than a cause, of eusociality. We tested this idea with a comparative analysis of female mating frequencies in 267 species of eusocial bees, wasps, and ants. We found that mating with a single male, which maximizes relatedness, is ancestral for all eight independent eusocial lineages that we investigated. Mating with multiple males is always derived. Furthermore, we found that high polyandry ( effective mates) occurs only in lineages whose workers have lost reproductive totipotency. These results provide the first evidence that monogamy was critical in the evolution of eusociality, strongly supporting the prediction of inclusive fitness theory.
Publisher: The Royal Society
Date: 23-09-2009
Abstract: Recruitment via pheromone trails by ants is arguably one of the best-studied ex les of self-organization in animal societies. Yet it is still unclear if and how trail recruitment allows a colony to adapt to changes in its foraging environment. We study foraging decisions by colonies of the ant Pheidole megacephala under dynamic conditions. Our experiments show that P. megacephala , unlike many other mass recruiting species, can make a collective decision for the better of two food sources even when the environment changes dynamically. We developed a stochastic differential equation model that explains our data qualitatively and quantitatively. Analysing this model reveals that both deterministic and stochastic effects (noise) work together to allow colonies to efficiently track changes in the environment. Our study thus suggests that a certain level of noise is not a disturbance in self-organized decision-making but rather serves an important functional role.
Publisher: Elsevier BV
Date: 05-2010
DOI: 10.1016/J.TREE.2009.12.001
Abstract: Recent evidence for genetic effects on royal and worker caste differentiation from erse social insect taxa has put an end to the view that these phenotypes stem solely from a developmental switch controlled by environmental factors. Instead, the relative influences of genotypic and environmental effects on caste vary among species, ranging from largely environmentally controlled phenotypes to almost purely genetic systems. Disentangling the selective forces that generate variation for caste predisposition will require characterizing the genetic mechanisms underlying this variation, and identifying particular life-history strategies and kin structures associated with strong genetic effects on caste.
Publisher: Elsevier BV
Date: 08-2014
Publisher: Springer Science and Business Media LLC
Date: 09-2003
Publisher: Elsevier BV
Date: 06-2003
Publisher: Annual Reviews
Date: 2008
DOI: 10.1146/ANNUREV.ENTO.53.103106.093515
Abstract: One of the most obvious characteristics of an insect society is reproductive cooperation. Yet insect colonies are vulnerable to reproductive parasitism, both by workers from their own colony and by workers from others. Little is known about the mechanisms insect societies have evolved to protect themselves from being exploited from within and outside the colony and the mechanisms that social parasites have evolved to circumvent these mechanisms. Here we showcase recently discovered cases of intraspecific parasitism by workers in eusocial bees. These discoveries overturn the widespread view that insect colonies are like fortresses populated by female eunuchs, and yield important insights into the mechanisms that normally enforce functional worker sterility.
Publisher: Oxford University Press (OUP)
Date: 20-12-2007
Publisher: Elsevier BV
Date: 12-2012
Publisher: Wiley
Date: 23-09-2009
Publisher: Elsevier BV
Date: 12-2012
Publisher: Springer Science and Business Media LLC
Date: 03-2002
Publisher: Test accounts
Date: 1998
Publisher: American Society for Microbiology
Date: 15-08-2017
DOI: 10.1128/JVI.00158-17
Abstract: Understanding the ersity and consequences of viruses present in honey bees is critical for maintaining pollinator health and managing the spread of disease. The viral landscape of honey bees ( Apis mellifera ) has changed dramatically since the emergence of the parasitic mite Varroa destructor , which increased the spread of virulent variants of viruses such as deformed wing virus. Previous genomic studies have focused on colonies suffering from infections by Varroa and virulent viruses, which could mask other viral species present in honey bees, resulting in a distorted view of viral ersity. To capture the viral ersity within colonies that are exposed to mites but do not suffer the ultimate consequences of the infestation, we examined populations of honey bees that have evolved naturally or have been selected for resistance to Varroa . This analysis revealed seven novel viruses isolated from honey bees s led globally, including the first identification of negative-sense RNA viruses in honey bees. Notably, two rhabdoviruses were present in three geographically erse locations and were also present in Varroa mites parasitizing the bees. To characterize the antiviral response, we performed deep sequencing of small RNA populations in honey bees and mites. This provided evidence of a Dicer-mediated immune response in honey bees, while the viral small RNA profile in Varroa mites was novel and distinct from the response observed in bees. Overall, we show that viral ersity in honey bee colonies is greater than previously thought, which encourages additional studies of the bee virome on a global scale and which may ultimately improve disease management. IMPORTANCE Honey bee populations have become increasingly susceptible to colony losses due to pathogenic viruses spread by parasitic Varroa mites. To date, 24 viruses have been described in honey bees, with most belonging to the order Picornavirales . Collapsing Varroa -infected colonies are often overwhelmed with high levels of picornaviruses. To examine the underlying viral ersity in honey bees, we employed viral metatranscriptomics analyses on three geographically erse Varroa- resistant populations from Europe, Africa, and the Pacific. We describe seven novel viruses from a range of erse viral families, including two viruses that are present in all three locations. In honey bees, small RNA sequences indicate that these viruses are processed by Dicer and the RNA interference pathway, whereas Varroa mites produce strikingly novel small RNA patterns. This work increases the number and ersity of known honey bee viruses and will ultimately contribute to improved disease management in our most important agricultural pollinator.
Publisher: Springer Science and Business Media LLC
Date: 11-10-2017
Publisher: Springer Science and Business Media LLC
Date: 28-07-2005
DOI: 10.1007/S00359-005-0035-Z
Abstract: Honey bee workers maintain the brood nest of their colony within a narrow temperature range of 34.5+/-1.5 degrees C, implying that there are significant fitness costs if brood is reared outside the normal range. However, the effects of abnormal incubation temperatures are subtle and not well documented. Here we show that short-term learning and memory abilities of adult workers are affected by the temperature they experienced during pupal development. In contrast, long-term learning and memory is not significantly affected by rearing temperature. Furthermore, we could detect no effects of incubation temperature on fluctuating asymmetry, as a measure of developmental stability, in workers, queens or drones. We conclude that the most important consequence of abnormal rearing temperatures are subtle neural deficiencies affecting short-term memory rather than physical abnormalities.
Publisher: Elsevier BV
Date: 1988
Publisher: Oxford University Press (OUP)
Date: 20-07-2011
Abstract: Unmated workers of the Cape honeybee Apis mellifera capensis can produce female offspring including daughter queens. As worker-laid queens are produced asexually, we wondered whether these asexually produced in iduals reproduce asexually or sexually. We s led 11 colonies headed by queens known to be the clonal offspring of workers and genotyped 23 worker offspring from each queen at 5 microsatellite loci. Without exception, asexually produced queens produced female worker offspring sexually. In addition, we report the replacement of a queen by her asexually produced granddaughter, with this asexually produced queen also producing offspring sexually. Hence, once a female larva is raised as a queen, mating and sexual reproduction appears to be obligatory in this subspecies, despite the fact that worker-laid queens are derived from asexual lineages.
Publisher: Springer Science and Business Media LLC
Date: 07-11-2016
Abstract: Some invasive hymenopteran social insects found new populations with very few reproductive in iduals. This is despite the high cost of founder effects for such insects, which generally require heterozygosity at a single locus-the complementary sex determiner, csd-to develop as females. In iduals that are homozygous at csd develop as either infertile or subfertile diploid males or not at all. Furthermore, diploid males replace the female workers that are essential for colony function. Here we document how the Asian honey bee (Apis cerana) overcame the diploid male problem during its invasion of Australia. Natural selection prevented the loss of rare csd alleles due to genetic drift and corrected the skew in allele frequencies caused by founder effects to restore high average heterozygosity. Thus, balancing selection can alleviate the genetic load at csd imposed by severe bottlenecks, and so facilitate invasiveness.
Publisher: Wiley
Date: 12-2004
Publisher: Springer Science and Business Media LLC
Date: 05-06-2008
Publisher: Elsevier BV
Date: 11-2011
Publisher: Oxford University Press (OUP)
Date: 05-2019
Publisher: Springer Science and Business Media LLC
Date: 08-2002
Publisher: Test accounts
Date: 1998
Publisher: Elsevier
Date: 2009
Publisher: Oxford University Press (OUP)
Date: 10-2018
Abstract: The haplodiploid system of sex determination of Hymenoptera acts as an exaptation for species to evolve novel forms of asexual reproduction including thelytoky (clonal offspring of the mother). During normal reproduction in Hymenoptera, three of the four products of meiosis that are present in newly-laid eggs are lost as polar bodies, while the remaining pronucleus either develops as a haploid male or fuses with a sperm nucleus to produce a diploid zygote. In contrast, in thelytokous reproduction, which is uncommon but taxonomically widespread, two of the four products of meiosis fuse, as if one acted as a sperm. Queenless workers of Apis mellifera capensis, a subspecies of honey bee from South Africa, routinely reproduce thelytokously. Unmated A. m. capensis queens can also be induced to lay thelytokously by narcosis with carbon dioxide, but mated queens are never thelytokous. We artificially inseminated A. m. capensis queens using CO2 narcosis. Up to 1/3 of offspring workers carried two maternal alleles and an allele of one father whereas no three-allele progeny were seen in control queens of the arrhenotokous (unfertilized eggs result in males) subspecies A. m. scutellata. Flow cytometry of three-allele in iduals revealed that they were triploid and arose from the fertilization of a thelytokous fusion nucleus. We then reared six queens from a narcotized A. m. capensis queen and determined the ploidy of the offspring queens based on microsatellites. One of the five daughters was triploid. Following artificial insemination, this queen produced unfertilized thelytokous diploid eggs at high frequency, and unfertilized triploid eggs at much lower frequency. If fertilized, thelytokous diploid eggs were non-viable, even though triploidy in itself does not impede normal development. In contrast, when the rarer triploid eggs were fertilized, a proportion developed into viable tetraploids. Our study highlights the extraordinary developmental flexibility of haplo-diploid systems.
Publisher: Springer Science and Business Media LLC
Date: 18-07-2008
Publisher: Wiley
Date: 06-2009
Publisher: Oxford University Press (OUP)
Date: 17-10-2014
Publisher: The Royal Society
Date: 09-06-2021
Abstract: 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.
Publisher: Elsevier BV
Date: 03-2013
Publisher: Wiley
Date: 2010
DOI: 10.1890/09-0358.1
Abstract: How in iduals deal with multiple conflicting demands is an important aspect of foraging ecology, yet work on foraging behavior has typically neglected neurologically simple organisms. Here we examine the impact of an abiotic risk (light) and energetic status on the foraging decisions of a protist, the slime mold Physarum polycephalum. We examined patch choice in a "non-risky" environment by presenting starved and non-starved P. polycephalum amoebas with a choice between two shaded food patches (one high quality, one low quality). We next examined patch choice in the presence of a conflict between foraging risk (light exposure) and food quality by presenting amoebas with a choice between a shaded, low-quality patch, and a light-exposed, high-quality patch. When both patches were shaded, 100% of amoebas selected the higher quality food patch, irrespective of food-quality differences or the in idual's energetic status. When light exposure and food quality conflicted, amoebas selected the patch with the higher food quality when the quality difference between the patches was high. When the quality difference between patches was small, amoebas selected the shaded, lower quality patch.
Publisher: Wiley
Date: 08-2017
DOI: 10.1111/EVO.13291
Abstract: Although the uniparental (or maternal) inheritance of mitochondrial DNA (mtDNA) is widespread, the reasons for its evolution remain unclear. Two main hypotheses have been proposed: selection against in iduals containing different mtDNAs (heteroplasmy) and selection against "selfish" mtDNA mutations. Recently, uniparental inheritance was shown to promote adaptive evolution in mtDNA, potentially providing a third hypothesis for its evolution. Here, we explore this hypothesis theoretically and ask if the accumulation of beneficial mutations provides a sufficient fitness advantage for uniparental inheritance to invade a population in which mtDNA is inherited biparentally. In a deterministic model, uniparental inheritance increases in frequency but cannot replace biparental inheritance if only a single beneficial mtDNA mutation sweeps through the population. When we allow successive selective sweeps of mtDNA, however, uniparental inheritance can replace biparental inheritance. Using a stochastic model, we show that a combination of selection and drift facilitates the fixation of uniparental inheritance (compared to a neutral trait) when there is only a single selective mtDNA sweep. When we consider multiple mtDNA sweeps in a stochastic model, uniparental inheritance becomes even more likely to replace biparental inheritance. Our findings thus suggest that selective sweeps of beneficial mtDNA haplotypes can drive the evolution of uniparental inheritance.
Publisher: Springer Science and Business Media LLC
Date: 03-02-2017
Publisher: The Royal Society
Date: 12-2011
Abstract: While studies of sexual selection focus primarily on female choice and male–male competition, males should also exert mate choice in order to maximize their reproductive success. We examined male mate choice in mosquitofish, Gambusia holbrooki , with respect to female size and female dominance. We found that the number of mating attempts made by a male was predicted by the dominance rank of females in a group, with dominant females attracting more mating attempts than subordinates. The number of mating attempts made by males was independent of the female size. The observed bias in the number of mating attempts towards dominant females may be driven either by straightforward male mate choice, since dominance and female fecundity are often closely related, or via the dominant females mediating male mating behaviour by restricting their access to subordinate females.
Publisher: Frontiers Media SA
Date: 17-02-2015
Publisher: Oxford University Press (OUP)
Date: 28-02-2008
Abstract: When workers of the thelytokous Cape honeybee, Apis mellifera capensis, come into contact with colonies of the neighboring arrhenotokous subspecies Apis mellifera scutellata, they can become lethal social parasites. We examined the inheritance of 3 traits (number of ovarioles, number of basitarsal hairs, and size of spermatheca) that are thought to be associated with reproductive potential in A. m. capensis workers. To do so, we produced hybrid A. m. scutellata/A. m. capensis queens and backcrossed them to either A. m. capensis or A. m. scutellata drones. We then measured the 3 traits in parental, hybrid, and backcross offspring. We show that the 3 traits are phenotypically correlated. We also show that the expression of ovariole number, basitarsal hairs, and size of spermatheca is influenced by the genotype of the in idual and the rearing environment but that the influence of the rearing environment is less important to the number of ovarioles. We hypothesize a single recessive allele (l), present at high frequency in natural A. m. capensis populations, which when homozygous causes larvae to elicit more food. This increased feeding as larvae causes resulting adult workers to develop more queen-like morphology and increased reproductive potential. The number of ovarioles, in contrast, appears to be under independent genetic control.
Publisher: Elsevier BV
Date: 08-2003
Publisher: Springer Science and Business Media LLC
Date: 05-05-2017
Publisher: Elsevier BV
Date: 02-2015
Publisher: The Company of Biologists
Date: 2011
DOI: 10.1242/JEB.048173
Abstract: Natural systems are a source of inspiration for computer algorithms designed to solve optimisation problems. Yet most ‘nature-inspired’ algorithms take only superficial inspiration from biology, and little is known about how real biological systems solve difficult problems. Moreover, ant algorithms, neural networks and similar methods are usually applied to static problems, whereas most biological systems have evolved to perform under dynamically changing conditions. We used the Towers of Hanoi puzzle to test whether Argentine ants can solve a potentially difficult optimisation problem. We also tested whether the ants can adapt to dynamic changes in the problem. We mapped all possible solutions to the Towers of Hanoi on a single graph and converted this into a maze for the ants to solve. We show that the ants are capable of solving the Towers of Hanoi, and are able to adapt when sections of the maze are blocked off and new sections installed. The presence of exploration pheromone increased the efficiency of the resulting network and increased the ants' ability to adapt to changing conditions. Contrary to previous studies, our study shows that mass-recruiting ant species such as the Argentine ant can forage effectively in a dynamic environment. Our results also suggest that novel optimisation algorithms can benefit from stronger biological mimicry.
Publisher: Springer Science and Business Media LLC
Date: 30-05-2007
Publisher: Cold Spring Harbor Laboratory
Date: 28-08-2023
DOI: 10.1101/2023.08.26.554974
Abstract: Deformed wing virus (DWV), in association with Varroa destructor , is currently the leading factor associated with global honey bee deaths. With the exception of Australia, the virus and mite have a near global distribution, making it difficult to separate the effect of one from the other. Over time, the prevalence of the two main DWV genotypes (DWV-A and DWV-B) has changed, leading to the suggestion that the two strains elicit a different immune response by the host, the western honey bee Apis mellifera . Here we use a honey bee population naive to both the mite and the virus to investigate if honey bees show a different immunological response to DWV genotypes. We examined the expression of 19 immune genes by RT-qPCR and comprehensively analysed the small RNA response in honey bees after experimental injection with DWV-A and DWV-B. We found no evidence to indicate that DWV-A and DWV-B elicit a different immune response in honey bees. We found that RNA interference genes are up-regulated during DWV infection and that the small interfering RNA (siRNA) response is proportional to viral loads, yet does not inhibit the virus from accumulating to high loads. We also found that the siRNA response towards DWV was weaker than the response to another honey bee pathogen, Black queen cell virus. This suggests that DWV is comparatively better at evading antiviral host defences. There was no evidence for the production of virus-derived PIWI-RNAs in response to DWV infection. In contrast to previous studies, and in the absence of V. destructor , we found no evidence that DWV has an immunosuppressive effect in honey bees. Overall, our results advance our understanding of the immunological effect DWV elicits in honey bees.
Publisher: The Royal Society
Date: 19-10-2016
Abstract: Darwin was the first to recognize that sexual selection is a strong evolutionary force. Exaggerated traits allow same-sex in iduals to compete over access to mates and provide a mechanism by which mates are selected. It is relatively easy to appreciate how inter- and intrasexual selection work in organisms with the sensory capabilities to perceive physical or behavioural traits that signal mate quality or mate compatibility, and to assess the relative quality of competitors. It is therefore not surprising that most studies of sexual selection have focused on animals with separate sexes and obvious adaptations that function in the context of reproductive competition. Yet, many sexual organisms are both male and female at the same time, often lack sexual dimorphism and never come into direct contact at mating. How does sexual selection act in such species, and what can we learn from them? Here, we address these questions by exploring the potential for sexual selection in simultaneous hermaphrodites, sperm- and broadcast spawners, plants and fungi. Our review reveals a range of mechanisms of sexual selection, operating primarily after gametes have been released, which are common in many of these groups and also quite possibly in more familiar (internally fertilizing and sexually dimorphic) organisms. This article is part of the themed issue ‘Weird sex: the underappreciated ersity of sexual reproduction’.
Publisher: Oxford University Press (OUP)
Date: 22-03-2014
Publisher: Oxford University Press (OUP)
Date: 25-12-2016
Publisher: Wiley
Date: 08-2000
Publisher: Elsevier
Date: 2009
Publisher: Elsevier BV
Date: 08-2019
DOI: 10.1016/J.COIS.2019.03.009
Abstract: In contrast to human societies, where kings and queens can be sources of conflict, we argue that the morphologically distinct queens of insect colonies are central to the minimization of conflict within their societies. Thus, the evolution of irreversible queen and worker castes represents a major transition in social evolution. Queens are selected to become better reproducers, and workers are selected to become better workers. The reproductive success of queens and workers are, therefore, inextricably linked. Workers achieve reproductive success by assisting the queen, whereas the queen needs her workers to provide her with the wherewithal to raise her brood. The tighter the mutual dependence, the lower conflict, and the larger insect societies can become. As the queen becomes a better breeder, workers are selected to become better at raising their siblings. Yet, nothing in nature is ever free of conflict and with the evolution of a true worker caste a new set of conflicts arises. Multiple mating by queens in particular opens the door to a new set of conflicts. Ironically, multiple mating can only evolve once within-colony conflict is reduced by evolving a true worker caste.
Publisher: Test accounts
Date: 1999
Publisher: Frontiers Media SA
Date: 07-01-2016
Publisher: Springer Science and Business Media LLC
Date: 19-03-2016
Publisher: Wiley
Date: 26-03-2003
Publisher: Springer Science and Business Media LLC
Date: 21-10-2004
DOI: 10.1007/S00114-004-0576-Y
Abstract: Worker-policing is a well-documented mechanism that maintains functional worker sterility in queen-right honey-bee colonies. Unknown, however, is the source of the egg-marking signal that is thought to be produced by the queen and used by policing workers to discriminate between queen- and worker-laid eggs. Here we investigate whether mating is necessary for the queen to produce the egg-marking signal. We compare the removal rate of eggs laid by virgin queens and compare this rate with that of eggs laid by mated queens. Our results show that mating does not affect the acceptability of eggs, suggesting that physiological changes linked to the act of mating do not play a role in the production of the queen's egg-marking signal.
Publisher: The Royal Society
Date: 06-10-2013
Abstract: Reproductive swarms of honeybees are faced with the problem of finding a good site to establish a new colony. We examined the potential effects of swarm size on the quality of nest-site choice through a combination of modelling and field experiments. We used an in idual-based model to examine the effects of swarm size on decision accuracy under the assumption that the number of bees actively involved in the decision-making process (scouts) is an increasing function of swarm size. We found that the ability of a swarm to choose the best of two nest sites decreases as swarm size increases when there is some time-lag between discovering the sites, consistent with Janson & Beekman (Janson & Beekman 2007 Proceedings of European Conference on Complex Systems , pp. 204–211.). However, when simulated swarms were faced with a realistic problem of choosing between many nest sites discoverable at all times, larger swarms were more accurate in their decisions than smaller swarms owing to their ability to discover nest sites more rapidly. Our experimental fieldwork showed that large swarms invest a larger number of scouts into the decision-making process than smaller swarms. Preliminary analysis of waggle dances from experimental swarms also suggested that large swarms could indeed discover and advertise nest sites at a faster rate than small swarms.
Publisher: The Company of Biologists
Date: 2014
DOI: 10.1242/JEB.103283
Abstract: During reproductive swarming honey bee scouts perform two very important functions. Firstly, they find new nesting locations and return to the swarm cluster to communicate their discoveries. Secondly, once the swarm is ready to depart informed scout bees act as guides, leading the swarm to its final destination. We have previously hypothesised that the two processes, selecting a new nest site and swarm guidance, are tightly linked in honey bees. When swarms can be laissez faire about where they nest, reaching directional consensus prior to lift off seems unnecessary. If, on the other hand, it is essential that the swarm reaches a precise location, either directional consensus must be near unanimous prior to swarm departure or only a select subgroup of the scouts attempts to guide the swarm. Here we test experimentally if directional consensus is necessary for the successful guidance of swarms of the Western honey bee Apis mellifera by forcing swarms to the air prior to the completion of the decision-making process. Our results show that swarms were unable to guide themselves prior to the swarm reaching the pre-flight buzzing phase of the decision-making process, even when directional consensus was high. We therefore conclude that most likely not all scouts involved in the decision-making process attempt to guide the swarm.
Publisher: Springer Science and Business Media LLC
Date: 24-04-2015
Publisher: IOP Publishing
Date: 21-09-2017
Publisher: Public Library of Science (PLoS)
Date: 16-04-2015
Publisher: Oxford University Press (OUP)
Date: 21-02-2017
Publisher: The Royal Society
Date: 28-11-2008
Abstract: The Cape bee ( Apis mellifera capensis ) is unique among honeybees in that workers can lay eggs that instead of developing into males develop into females via thelytokous parthenogenesis. We show that this ability allows workers to compete directly with the queen over the production of new queens. Genetic analyses using microsatellites revealed that 23 out of 39 new queens produced by seven colonies were offspring of workers and not the resident queen. Of these, eight were laid by resident workers, but the majority were offspring of parasitic workers from other colonies. The parasites were derived from several clonal lineages that entered the colonies and successfully targeted queen cells for parasitism. Hence, these parasitic workers had the potential to become genetically reincarnated as queens. Of the daughter queens laid by the resident queen, three were produced asexually, suggesting that queens can ‘choose’ to produce daughter queens clonally and thus have the potential for genetic immortality.
Publisher: Elsevier BV
Date: 11-2015
DOI: 10.1016/J.JMB.2015.07.007
Abstract: Because of its peculiar biology and the ease with which it can be cultured, the acellular slime mould Physarum polycephalum has long been a model organism in a range of disciplines. Due to its macroscopic, syncytial nature, it is no surprise that it has been a favourite amongst cell biologists. Its inclusion in the experimental tool kit of behavioural ecologists is much more recent. These recent studies have certainly paid off. They have shown that, for an organism that lacks a brain or central nervous system, P. polycephalum shows rather complex behaviour. For ex le, it is capable of finding the shortest path through a maze, it can construct networks as efficient as those designed by humans, it can solve computationally difficult puzzles, it makes multi-objective foraging decisions, it balances its nutrient intake and it even behaves irrationally. Are the slime mould's achievements simply "cute", worthy of mentioning in passing but nothing to take too seriously? Or do they hint at the fundamental processes underlying all decision making? We will address this question after reviewing the decision-making abilities of the slime mould.
Publisher: Public Library of Science (PLoS)
Date: 04-03-2008
Publisher: Springer Science and Business Media LLC
Date: 21-12-2014
Publisher: SAGE Publications
Date: 30-01-2019
Abstract: Although human decision making seems complex, there is evidence that many decisions are grounded in simple heuristics. Such heuristic models of decision making are widespread in nature. To understand how and why different forms of information processing evolve, it is insightful to study the minimal requirements for cognition. Here, we explore the minimally cognitive behaviour of the acellular slime mould, Physarum polycephalum, in order to discuss the ecological pressures that lead to the development of information processing mechanisms. We discuss evidence for memory, basic forms of learning and economically irrational choice in P. polycephalum. We compare P. polycephalum’s behaviour with a number of other non-neuronal organisms in order to question the evolutionary need for complex nervous systems to develop cognitive traits. By highlighting a few ex les of common mechanisms, we conclude that all organisms contain the building blocks for more complex information processing. Returning the debate about cognition to the biological basics demystifies some of the confusion around the term ‘cognition’.
Publisher: Springer Science and Business Media LLC
Date: 2002
DOI: 10.1038/415163A
Publisher: The Company of Biologists
Date: 08-2009
DOI: 10.1242/JEB.029827
Abstract: In this paper we investigate the foraging activity of an invasive ant species, the big headed ant Pheidole megacephala. We establish that the ants' behavior is consistent with the use of two different pheromone signals, both of which recruit nestmates. Our experiments suggest that during exploration the ants deposit a long-lasting pheromone that elicits a weak recruitment of nestmates, while when exploiting food the ants deposit a shorter lasting pheromone eliciting a much stronger recruitment. We further investigate experimentally the role of these pheromones under both static and dynamic conditions and develop a mathematical model based on the hypothesis that exploration locally enhances exploitation, while exploitation locally suppresses exploration. The model and the experiments indicate that exploratory pheromone allows the colony to more quickly mobilize foragers when food is discovered. Furthermore, the combination of two pheromones allows colonies to track changing foraging conditions more effectively than would a single pheromone. In addition to the already known causes for the ecological success of invasive ant species, our study suggests that their opportunistic strategy of rapid food discovery and ability to react to changes in the environment may have strongly contributed to their dominance over native species.
Publisher: Oxford University Press (OUP)
Date: 14-02-2017
Publisher: Elsevier BV
Date: 10-2004
DOI: 10.1016/J.TREE.2004.07.008
Abstract: When Queen Elizabeth is at home in Buckingham Palace, tradition has it that the Royal Standard is raised, so that all may know the fact. Although it is not crucial for most of us to know whether Her Majesty is home, it is in social insects. Endler et al. have recently shown how an ant queen signals her presence to her remote workers: she marks her eggs. This is significant because it provides insight into how queens maintain reproductive monopoly within their colonies.
Publisher: Springer Science and Business Media LLC
Date: 10-2002
DOI: 10.1007/S00114-002-0365-4
Abstract: In the Cape honey bee Apis mellifera capensis, workers lay female eggs without mating by thelytokous parthenogenesis. As a result, workers are as related to worker-laid eggs as they are to queen-laid eggs and therefore worker policing is expected to be lower, or even absent. This was tested by transferring worker- and queen-laid eggs into three queenright A. m. capensis discriminator colonies and monitoring their removal. Our results show that worker policing is variable in A. m. capensis and that in one colony worker-laid eggs were not removed. This is the first report of a non-policing queenright honey bee colony. DNA microsatellite and morphometric analysis suggests that the racial composition of the three discriminator colonies was different. The variation in policing rates could be explained by differences in degrees of hybridisation between A. m. capensis and A. m. scutellata, although a larger survey is needed to confirm this.
Publisher: Wiley
Date: 08-1998
Publisher: The Royal Society
Date: 22-01-2013
Abstract: Apis mellifera capensis is unique among honeybees in that unmated workers can produce pseudo-clonal female offspring via thelytokous parthenogenesis. Workers use this ability to compete among themselves and with their queen to be the mother of new queens. Males could therefore enhance their reproductive success by imprinting genes that enhance fertility in their daughter workers. This possibility sets the scene for intragenomic conflict between queens and drones over worker reproductive traits. Here, we show a strong parent-of-origin effect for ovary size (number of ovarioles) in reciprocal crosses between two honeybee subspecies, A. m. capensis and Apis mellifera scutellata. In this cross, workers with an A. m. capensis father had 30% more ovarioles than genotypically matched workers with an A. m. scutellata father. Other traits we measured (worker weight at emergence and the presence/absence of a spermatheca) are influenced more by rearing conditions than by parent-of-origin effects. Our study is the first to show a strong epigenetic (or, less likely, cytoplasmic maternal) effect for a reproductive trait in the honeybee and suggests that a search for parent-of-origin effects in other social insects may be fruitful.
Publisher: Springer Science and Business Media LLC
Date: 08-05-2017
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.PLREV.2019.07.002
Abstract: We look at a recent expansion of Physarum research from inspiring biomimetic algorithms to serving as a model organism in the evolutionary study of perception, memory, learning, and decision making.
Publisher: Oxford University Press (OUP)
Date: 09-2008
DOI: 10.1534/GENETICS.108.090415
Abstract: The subspecies of honeybee indigenous to the Cape region of South Africa, Apis mellifera capensis, is unique because a high proportion of unmated workers can lay eggs that develop into females via thelytokous parthenogenesis involving central fusion of meiotic products. This ability allows pseudoclonal lineages of workers to establish, which are presently widespread as reproductive parasites within the honeybee populations of South Africa. Successful long-term propagation of a parthenogen requires the maintenance of heterozygosity at the sex locus, which in honeybees must be heterozygous for the expression of female traits. Thus, in successful lineages of parasitic workers, recombination events are reduced by an order of magnitude relative to meiosis in queens of other honeybee subspecies. Here we show that in unmated A. m. capensis queens treated to induce oviposition, no such reduction in recombination occurs, indicating that thelytoky and reduced recombination are not controlled by the same gene. Our virgin queens were able to lay both arrhenotokous male-producing haploid eggs and thelytokous female-producing diploid eggs at the same time, with evidence that they have some voluntary control over which kind of egg was laid. If so, they are able to influence the kind of second- ision meiosis that occurs in their eggs post partum.
Publisher: The Royal Society
Date: 31-08-2003
Abstract: Inclusive fitness theory has been very successful in predicting and explaining much of the observed variation in the reproductive characteristics of insect societies. For ex le, the theory correctly predicts sex–ratio biasing by workers in relation to the queen's mating frequency. However, within an insect society there are typically multiple reproductive optima, each corresponding to the interest of different in idual(s) or parties of interest. When multiple optima occur, which party's interests prevail? Presumably, the interests of the party with the greatest ‘power’ the ability to do or act. This article focuses on factors that influence power over colony reproduction. In particular, we seek to identify the principles that may cause different parties of interest to have greater or lesser power. In doing this, we discuss power from two different angles. On the one hand, we discuss general factors based upon non–idiosyncratic biological features (e.g. information, access to and ability to process food) that are likely to be important to all social Hymenoptera. On the other hand, we discuss idiosyncratic factors that depend upon the biology of a taxon at any hierarchical level. We propose that a better understanding of the ersity of reproductive characteristics of insect societies will come from combining inclusive fitness theory with a wide range of other factors that affect relative power in a conflict situation.
Publisher: Springer Science and Business Media LLC
Date: 11-01-2007
Publisher: Wiley
Date: 24-02-2014
DOI: 10.1111/MEC.12669
Abstract: Reproductive isolation between closely related species is often incomplete. The Western honeybee, Apis mellifera, and the Eastern hive bee, Apis cerana, have been allopatric for millions of years, but are nonetheless similar in morphology and behaviour. During the last century, the two species were brought into contact anthropogenically, providing potential opportunities for interspecific matings. Hybrids between A. mellifera and A. cerana are inviable, so natural interspecific matings are of concern because they may reduce the viability of A. cerana and A. mellifera populations - two of the world's most important pollinators. We examined the mating behaviour of A. mellifera and A. cerana queens and drones from Caoba Basin, China and Cairns, Australia. Drone mating flight times overlap in both areas. Analysis of the spermathecal contents of queens with species-specific genetic markers indicated that in Caoba Basin, 14% of A. mellifera queens mated with at least one A. cerana male, but we detected no A. cerana queens that had mated with A. mellifera males. Similarly, in Cairns, no A. cerana queens carried A. mellifera sperm, but one-third of A. mellifera queens had mated with at least one A. cerana male. No hybrid embryos were detected in eggs laid by interspecifically mated A. mellifera queens in either location. However, A. mellifera queens artificially inseminated with A. cerana sperm produced inviable hybrid eggs or unfertilized drones. This suggests that reproductive interference will impact the viability of honeybee populations wherever A. cerana and A. mellifera are in contact.
Publisher: Elsevier BV
Date: 11-2001
Publisher: The Royal Society
Date: 02-2023
Abstract: In metazoans, the expression of key phenotypic traits is sensitive to two- and three-way interactions between variation in mitochondrial DNA, nuclear DNA and the external environment. Whether gene- by -environment interactions affect phenotypes in single-celled eukaryotes is poorly studied, except in a few species of yeast and fungi. We developed a genetic panel of the unicellular slime mould, Physarum polycephalum containing strains differing in mitochondrial and nuclear DNA haplotypes. The panel also included two strains harbouring a selfishly replicating mitochondrial-fusion (mF) plasmid that could affect phenotype expression. We assayed movement and growth rate differences among the strains across two temperature regimes: 24° and 28°C. We found that the slime mould's growth rate, but not movement, is affected by G × G × E interactions. Predictably, mtDNA × nDNA interactions significantly affected both traits. The inter-trait correlation across the strains in each temperature regime was positive. Surprisingly, the mF plasmid had no negative effects on our chosen traits. Our study is the first to demonstrate genetic regulation of phenotype expression in a unicellular slime mould. The genetic effect on phenotypes manifests via epistatic interactions with the thermal environment, thus shedding new light on the role of G × G × E interactions in trait evolution in protists.
Publisher: The Royal Society
Date: 30-01-2019
Abstract: The arrival of the ectoparasitic mite Varroa destructor on the western honeybee Apis mellifera saw a change in the ersity and prevalence of honeybee RNA viruses. One virus in particular, deformed wing virus (DWV) has become closely associated with V. destructor , leading many to conclude that V. destructor has affected viral virulence by changing the mode of transmission. While DWV is normally transmitted via feeding and faeces, V. destructor transmits viruses by direct injection. This change could have resulted in higher viral prevalence causing increased damage to the bees. Here we test the effect of a change in the mode of transmission on the composition and levels of honeybee RNA viruses in the absence of V. destructor . We find a rapid increase in levels of two viruses, sacbrood virus (SBV) and black queen cell virus (BQCV) after direct injection of viral extracts into honeybee pupae. In pupae injected with high levels of DWV extracted from symptomatic adult bees, DWV levels rapidly decline in the presence of SBV and BQCV. Further, we observe high mortality in honeybee pupae when injected with SBV and BQCV, whereas injecting pupae with high levels of DWV results in near 100% survival. Our results suggest a different explanation for the observed association between V. destructor and DWV. Instead of V. destructor causing an increase in DWV virulence, we hypothesize that direct virus inoculation, such as that mediated by a vector, quickly eliminates the most virulent honeybee viruses resulting in an association with less virulent viruses such as DWV.
Publisher: Springer Science and Business Media LLC
Date: 12-03-2016
Publisher: Proceedings of the National Academy of Sciences
Date: 07-08-2001
Abstract: The complex collective behavior seen in many insect societies strongly suggests that a minimum number of workers are required for these societies to function effectively. Here we investigated the transition between disordered and ordered foraging in the Pharaoh's ant. We show that small colonies forage in a disorganized manner, with a transition to organized pheromone-based foraging in larger colonies. We also show that when food sources are difficult to locate through independent searching, this transition is first-order and exhibits hysteresis, comparable to a first-order phase transition found in many physical systems. To our knowledge, this is the first experimental evidence of a behavioral phase transition between a maladaptive (disorganized) and an adaptive (organized) state.
Publisher: Springer Science and Business Media LLC
Date: 06-2008
Publisher: The Royal Society
Date: 19-10-2016
Publisher: Oxford University Press (OUP)
Date: 28-04-2006
Publisher: Elsevier BV
Date: 02-2004
Publisher: Cold Spring Harbor Laboratory
Date: 16-05-2018
DOI: 10.1101/323527
Abstract: While it is well-established that the ectoparasitic mite Varroa destructor is largely responsible for the widely-reported decline of populations of the Western honeybee Apis mellifera , the exact role the mite plays in honeybee health remains unclear. The last few years have seen a surge in studies associating RNA viruses vectored by the mite with the death of honeybee colonies. Varroa facilitates the spread of RNA viruses because it feeds on developing bee brood and transfers haemolymph from bee-to-bee. Such a change in transmission, from horizontal and vertical to vector-based, is predicted to lead to an increase in virulence of RNA viruses, thus potentially providing an explanation for the observed association between Varroa and certain viruses. Here we document the effect of changing the route of transmission of honeybee viruses contained in the haemolymph of honeybee pupae. We find that a change in mode of transmission rapidly increases viral titres of two honeybee viruses, Sacbrood virus (SBV) and Black queen cell virus (BQCV). This increase in viral titre is accompanied by an increase in virulence. In contrast, the virus most often associated with Varroa , Deformed wing virus (DWV), shows a reduction in viral titre in the presence of SBV and BQCV. In addition, DWV does not cause mortality to honeybee pupae in isolation. Most likely a change in mode of transmission due to the arrival of a vector quickly eliminates the most virulent honeybee viruses resulting in an association between Varroa and less virulent viruses such as DWV. Our work therefore provides empirical evidence for an alternative explanation for the widely-observed association between Varroa and DWV.
Publisher: Oxford University Press (OUP)
Date: 16-02-2012
Publisher: The Royal Society
Date: 05-07-2014
Abstract: The peculiar biology of mitochondrial DNA (mtDNA) potentially has detrimental consequences for organismal health and lifespan. Typically, eukaryotic cells contain multiple mitochondria, each with multiple mtDNA genomes. The high copy number of mtDNA implies that selection on mtDNA functionality is relaxed. Furthermore, because mtDNA replication is not strictly regulated, within-cell selection may favour mtDNA variants with a replication advantage, but a deleterious effect on cell fitness. The opportunities for selfish mtDNA mutations to spread are restricted by various organism-level adaptations, such as uniparental transmission, germline mtDNA bottlenecks, germline selection and, during somatic growth, regular alternation between fusion and fission of mitochondria. These mechanisms are all hypothesized to maintain functional mtDNA. However, the strength of selection for maintenance of functional mtDNA progressively declines with age, resulting in age-related diseases. Furthermore, organismal adaptations that most probably evolved to restrict the opportunities for selfish mtDNA create secondary problems. Owing to predominantly maternal mtDNA transmission, recombination among mtDNA from different in iduals is highly restricted or absent, reducing the scope for repair. Moreover, maternal inheritance precludes selection against mtDNA variants with male-specific effects. We finish by discussing the consequences of life-history differences among taxa with respect to mtDNA evolution and make a case for the use of microorganisms to experimentally manipulate levels of selection.
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.PLREV.2018.05.002
Abstract: Physarum polycephalum, a single-celled, multinucleate slime mould, is a seemingly simple organism, yet it exhibits quasi-intelligent behaviour during extension, foraging, and as it adapts to dynamic environments. For these reasons, Physarum is an attractive target for modelling with the underlying goal to uncover the physiological mechanisms behind the exhibited quasi-intelligence and/or to devise novel algorithms for solving complex computational problems. The recent increase in modelling studies on Physarum has prompted us to review the latest developments in this field in the context of modelling and computing alike. Specifically, we cover models based on (i) morphology, (ii) taxis, and (iii) positive feedback dynamics found in top-down and bottom-up modelling techniques. We also survey the application of each of these core features of Physarum to solving difficult computational problems with real-world applications. Finally, we highlight some open problems in the field and present directions for future research.
Publisher: Springer Science and Business Media LLC
Date: 07-03-2012
Publisher: University of Chicago Press
Date: 04-2006
DOI: 10.1086/501169
Abstract: The occurrence of polygyny and polyandry in social insects has long puzzled evolutionary biologists. If cooperation requires genetic relatedness, how do we explain the occurrence and maintenance of mechanisms that reduce the degree of relatedness among colony members? A much-discussed hypothesis states that genetically erse colonies are more resistant to parasitism than homogenous colonies because genetic ersity reduces the spread of a disease within a colony. However, as we will argue in this note, a necessary condition for the parasite hypothesis is that genetically heterogeneous colonies have a larger suite of parasites that are capable of infecting them. This implicit relationship is important because it implies that even if the cost per infection is reduced, this may not be sufficient to offset the increased rate of acquiring infections. The advantages of genetic heterogeneity as a defense against parasites thus may not be as big as commonly thought.
Publisher: The Royal Society
Date: 02-02-2011
Abstract: Many biological systems use extensive networks for the transport of resources and information. Ants are no exception. How do biological systems achieve efficient transportation networks in the absence of centralized control and without global knowledge of the environment? Here, we address this question by studying the formation and properties of inter-nest transportation networks in the Argentine ant ( Linepithema humile ). We find that the formation of inter-nest networks depends on the number of ants involved in the construction process. When the number of ants is sufficient and networks do form, they tend to have short total length but a low level of robustness. These networks are topologically similar to either minimum spanning trees or Steiner networks. The process of network formation involves an initial construction of multiple links followed by a pruning process that reduces the number of trails. Our study thus illuminates the conditions under and the process by which minimal biological transport networks can be constructed.
Publisher: Wiley
Date: 21-04-2016
DOI: 10.1111/AEN.12206
Publisher: Wiley
Date: 12-05-2021
Abstract: Global pollinator declines as a result of emerging infectious diseases are of major concern. Managed honeybees Apis mellifera are susceptible to numerous parasites and pathogens, many of which appear to be transmissible to sympatric non‐ Apis taxa. The ectoparasitic mite Varroa destructor is considered to be the most significant threat to honeybees due to its role in vectoring RNA viruses, particularly Deformed wing virus (DWV). Vector transmission of DWV has resulted in the accumulation of high viral loads in honeybees and is often associated with colony death. DWV has two main genotypes, A and B. DWV‐A was more prevalent during the initial phase of V. destructor establishment. In recent years, the global prevalence of DWV‐B has increased, suggesting that DWV‐B is better adapted to vector transmission than DWV‐A. We aimed to determine the role vector transmission plays in DWV genotype prevalence at a colony level. We experimentally increased or decreased the number of V. destructor mites in honeybee colonies, and tracked DWV‐A and DWV‐B loads over a period of 10 months. Our results show that the two DWV genotypes differ in their response to mite numbers. DWV‐A accumulation in honeybees was positively correlated with mite numbers yet DWV‐A was largely undetected in the absence of the mite. In contrast, colonies had high loads of DWV‐B even when mite numbers were low. DWV‐B loads persisted in miticide‐treated colonies, indicating that this genotype has a competitive advantage over DWV‐A irrespective of mite numbers. Our findings suggest that the global increase in DWV‐B prevalence is not driven by selective pressure by the vector. Rather, DWV‐B is able to persist in colonies at higher viral loads relative to DWV‐A in the presence and absence of V. destructor . The interplay between V. destructor and DWV genotypes within honeybee colonies may have broad consequences upon viral ersity in sympatric taxa as a result of spillover.
Publisher: Elsevier BV
Date: 07-2009
Publisher: Wiley
Date: 02-2000
Publisher: Elsevier BV
Date: 2006
Publisher: Elsevier BV
Date: 07-2014
Publisher: Proceedings of the National Academy of Sciences
Date: 08-10-2012
Abstract: Spatial memory enhances an organism’s navigational ability. Memory typically resides within the brain, but what if an organism has no brain? We show that the brainless slime mold Physarum polycephalum constructs a form of spatial memory by avoiding areas it has previously explored. This mechanism allows the slime mold to solve the U-shaped trap problem—a classic test of autonomous navigational ability commonly used in robotics—requiring the slime mold to reach a chemoattractive goal behind a U-shaped barrier. Drawn into the trap, the organism must rely on other methods than gradient-following to escape and reach the goal. Our data show that spatial memory enhances the organism’s ability to navigate in complex environments. We provide a unique demonstration of a spatial memory system in a nonneuronal organism, supporting the theory that an externalized spatial memory may be the functional precursor to the internal memory of higher organisms.
Publisher: The Royal Society
Date: 11-02-2019
Abstract: Hamilton's theory of inclusive fitness provides a framework for understanding the evolution of social behaviour between kin, including parental and alloparental care. Brood parasitism is a reproductive tactic in which parasites exploit the care of other in iduals of the same species (conspecific parasitism) or different species (interspecific parasitism) to rear their brood. Here, drawing from ex les in birds and social insects, we identify two insights into brood parasitism that stem from inclusive fitness theory. First, the kin structure within nests, or between neighbouring nests, can create a niche space favouring the evolution of conspecific parasitism. For ex le, low average relatedness within social insect nests can increase selection for reproductive cheats. Likewise, high average relatedness between adjacent nests of some birds can increase a female's tolerance of parasitism by her neighbour. Second, intrabrood conflict will be high in parasitized broods, from the perspective of both parasite and host young, relative to unparasitized broods. We also discuss offspring recognition by hosts as an ex le of discrimination in a kin-selected social behaviour. We conclude that the inclusive fitness framework is instructive for understanding aspects of brood parasite and host evolution. In turn, brood parasites present some unique opportunities to test the predictions of inclusive fitness theory. This article is part of the theme issue ‘The coevolutionary biology of brood parasitism: from mechanism to pattern’.
Publisher: Springer Science and Business Media LLC
Date: 04-2000
DOI: 10.1038/35008148
Publisher: Elsevier BV
Date: 10-2014
Publisher: Oxford University Press (OUP)
Date: 27-03-2019
Publisher: Elsevier
Date: 2019
Publisher: Springer Science and Business Media LLC
Date: 23-10-2016
Publisher: The Company of Biologists
Date: 2013
DOI: 10.1242/JEB.081158
Abstract: Many biological systems require extensive networks to transport resources and information. Biological networks must trade-off network efficiency with the risk of network failure. Yet, biological networks develop in the absence of centralised control from the interactions of many components. Moreover, many biological systems need to be able to adapt when conditions change and the network requires modification. We used the slime mould Physarum polycephalum (Schwein) to study how the organism adapts its network after disruption. To allow us to determine the efficiency of the constructed networks, we used a well-known shortest path problem: the Towers of Hanoi maze. We first show that while P. polycephalum is capable of building networks with minimal length paths through the maze, most solutions are sub-optimal. We then disrupted the network by severing the main connecting path while opening a new path in the maze. In response to dynamic changes to the environment, P. polycephalum reconstructed more efficient solutions, with all replicates building networks with minimal length paths through the maze after network disruption. While P. polycephalum altered some of its existing network to accommodate changes in the environment, it also reconstructed large sections of the network from scratch. We compared the results obtained from P. polycephalum to those obtained using another distributed biological system: ant colonies. We hypothesise that network construction in ants hinges upon stronger positive feedback than for slime mould, ensuring ants converge more accurately upon the shortest path but are more constrained by the history of their networks in dynamic environments.
Publisher: Springer Science and Business Media LLC
Date: 03-03-2010
Publisher: Oxford University Press (OUP)
Date: 11-05-2012
Publisher: Elsevier BV
Date: 08-2012
DOI: 10.1016/J.JTBI.2012.04.003
Abstract: Ants live in dynamically changing environments, where food sources become depleted and alternative sources appear. Yet most mathematical models of ant foraging assume that the ants' foraging environment is static. Here we describe a mathematical model of ant foraging in a dynamic environment. Our model attempts to explain recent empirical data on dynamic foraging in the Argentine ant Linepithema humile (Mayr). The ants are able to find the shortest path in a Towers of Hanoi maze, a complex network containing 32,768 alternative paths, even when the maze is altered dynamically. We modify existing models developed to explain ant foraging in static environments, to elucidate what possible mechanisms allow the ants to quickly adapt to changes in their foraging environment. Our results suggest that navigation of in idual ants based on a combination of one pheromone deposited during foraging and directional information enables the ants to adapt their foraging trails and recreates the experimental results.
Publisher: The Company of Biologists
Date: 2015
DOI: 10.1242/JEB.116533
Abstract: Animals foraging in patchy, non- or slowly-renewing environments must make decisions about how long to remain within a patch. Organisms can use heuristics (‘rules of thumb’) based on available information to decide when to leave the patch. Here we investigate proximate patch departure heuristics in two species of giant, brainless amoeba: the slime moulds Didymium bahiense and Physarum polycephalum. We explicitly tested the importance of information obtained through experience by eliminating chemosensory cues of patch quality. In Physarum polycephalum, patch departure was influenced by the consumption of high, and to a much lesser extent low, quality food items such that engulfing a food item increased patch residency time. Physarum polycephalum also tended to forage for longer in darkened, ‘safe’ patches. In Didymium bahiense, engulfment of either a high or low quality food item increased patch residency irrespective of that food item's quality. Exposure to light had no effect on the patch residency time of D. bahiense. Given that our organisms lack a brain, our results illustrate how the use of simple heuristics can give the impression that in iduals make sophisticated foraging decisions.
Publisher: Springer Science and Business Media LLC
Date: 03-2002
Publisher: Springer Science and Business Media LLC
Date: 07-08-2017
Publisher: The Royal Society
Date: 26-03-2018
Abstract: During reproductive swarming, a honeybee swarm needs to decide on a new nest site and then move to the chosen site collectively. Most studies of swarming and nest-site selection are based on one species, Apis mellifera . Natural colonies of A. mellifera live in tree cavities. The quality of the cavity is critical to the survival of a swarm. Other honeybee species nest in the open, and have less strict nest-site requirements, such as the open-nesting dwarf honeybee Apis florea . Apis florea builds a nest comprised of a single comb suspended from a twig. For a cavity-nesting species, there is only a limited number of potential nest sites that can be located by a swarm, because suitable sites are scarce. By contrast, for an open-nesting species, there is an abundance of equally suitable twigs. While the decision-making process of cavity-nesting bees is geared towards selecting the best site possible, open-nesting species need to coordinate collective movement towards areas with potential nest sites. Here, we argue that the nest-site selection processes of A. florea and A. mellifera have been shaped by each species' specific nest-site requirements. Both species use the same behavioural algorithm, tuned to allow each species to solve their species-specific problem. This article is part of the theme issue ‘Collective movement ecology’.
Publisher: CRC Press
Date: 21-05-2009
Publisher: The Royal Society
Date: 05-07-2014
Abstract: Eukaryotic cells typically contain numerous mitochondria, each with multiple copies of their own genome, the mtDNA. Uniparental transmission of mitochondria, usually via the mother, prevents the mixing of mtDNA from different in iduals. While on the one hand, this should resolve the potential for selection for fast-replicating mtDNA variants that reduce organismal fitness, maternal inheritance will, in theory, come with another set of problems that are specifically relevant to males. Maternal inheritance implies that the mitochondrial genome is never transmitted through males, and thus selection can target only the mtDNA sequence when carried by females. A consequence is that mtDNA mutations that confer male-biased phenotypic expression will be prone to evade selection, and accumulate. Here, we review the evidence from the ecological, evolutionary and medical literature for male specificity of mtDNA mutations affecting fertility, health and ageing. While such effects have been discovered experimentally in the laboratory, their relevance to natural populations—including the human population—remains unclear. We suggest that the existence of male expression-biased mtDNA mutations is likely to be a broad phenomenon, but that these mutations remain cryptic owing to the presence of counter-adapted nuclear compensatory modifier mutations, which offset their deleterious effects.
Publisher: Test accounts
Date: 1999
Publisher: Springer Science and Business Media LLC
Date: 27-02-2008
Publisher: Springer Science and Business Media LLC
Date: 05-2004
Publisher: Elsevier
Date: 2019
Publisher: Springer Berlin Heidelberg
Publisher: The Royal Society
Date: 16-05-2005
Abstract: Worker policing, wherein social insect workers prevent their sisters from reproducing by eating worker-laid eggs, is recognized as a textbook ex le of kin selection in action. However, the evolutionary basis of policing was recently challenged in a study that suggested that police-workers remove worker-laid eggs not because rearing workers' sons reduces worker fitness, but merely because worker-laid eggs have low viability. Here, we refute Pirk et al. 's conclusions. First, we confirm earlier work that showed equal viability of eggs laid by queens and workers. Second, a statistical analysis of the data of Pirk et al. reveals that their own data do not support the conclusion that worker-laid eggs are policed merely because of their low viability. Third, we present data that unequivocally show that police-workers cannot discriminate between dead and live eggs. Hence, our study seriously weakens the challenge to the kin-selected basis of policing in honeybees.
Publisher: Oxford University Press (OUP)
Date: 18-04-2013
Publisher: Springer Science and Business Media LLC
Date: 09-11-2011
Publisher: Oxford University Press (OUP)
Date: 2009
No related grants have been discovered for Madeleine Beekman.