Edmunds M.,University of Central Lancashire |
EDgar J.A.,CSIRO |
Lawrence J.,Stellenbosch University |
Smith D.A.S.,Eton College
Biological Journal of the Linnean Society | Year: 2010
On two occasions, on opposite sides of the African continent (Cape Coast, Ghana, and Dar es Salaam, Tanzania), high adult population densities in the polymorphic butterfly Hypolimnas misippus (a presumed mimic of Danaus chrysippus) were followed by linkage disequilibrium in combinations of fore- and hindwing colour patterns. On both occasions, disequilibrium was caused by significant changes in morph frequencies favouring rarer and more mimetic forms. Recaptures were too few for analysis at Dar, although the changes there took place within a single generation and must have been the result of differential survival. Recapture rate data and survival rate estimates at Cape Coast support the hypothesis that selective predation was responsible, as does the observation of synchronous linkage disequilibrium at Dar in the model D. chrysippus, indicating parasitic mimicry. There was clear selection for the perfection of mimicry for forewings at Dar and for hindwings at Cape Coast. Disequilibrium is also reported for two other sites, Legon (Ghana) and Boksburg (South Africa) and, in all four sites, it was associated with an increase in the most mimetic forms. New chemical evidence is presented to support the contention that D. chrysippus is a defended model. Although all the evidence leads to the conclusion that H. misippus is a Batesian mimic of D. chrysippus, many questions remain, particularly with regard to the identity of predators, the episodic nature of selective predation events, and their apparent lack of lasting and significant impact on overall gene frequencies. We conclude that H. misippus presents both challenges and opportunities for studies on mimicry, and we suggest that linkage disequilibrium can be a useful generic indicator for Gestalt predation on polymorphic prey. © 2010 The Linnean Society of London.
PubMed | Emerging Infectious Diseases Laboratory, Insect Committee of Nature Kenya, University of Lübeck, Kenyatta University and 5 more.
Type: Journal Article | Journal: Proceedings. Biological sciences | Year: 2016
Sexually antagonistic selection can drive both the evolution of sex chromosomes and speciation itself. The tropical butterfly the African Queen, Danaus chrysippus, shows two such sexually antagonistic phenotypes, the first being sex-linked colour pattern, the second, susceptibility to a male-killing, maternally inherited mollicute, Spiroplasma ixodeti, which causes approximately 100% mortality in male eggs and first instar larvae. Importantly, this mortality is not affected by the infection status of the male parent and the horizontal transmission of Spiroplasma is unknown. In East Africa, male-killing of the Queen is prevalent in a narrow hybrid zone centred on Nairobi. This hybrid zone separates otherwise allopatric subspecies with different colour patterns. Here we show that a neo-W chromosome, a fusion between the W (female) chromosome and an autosome that controls both colour pattern and male-killing, links the two phenotypes thereby driving speciation across the hybrid zone. Studies of the population genetics of the neo-W around Nairobi show that the interaction between colour pattern and male-killer susceptibility restricts gene flow between two subspecies of D. chrysippus Our results demonstrate how a complex interplay between sex, colour pattern, male-killing, and a neo-W chromosome, has set up a genetic sink that keeps the two subspecies apart. The association between the neo-W and male-killing thus provides a smoking gun for an ongoing speciation process.
News Article | February 28, 2017
Carnegie Council for Ethics in International Affairs is delighted to announce the winners of its 2016 International Student/Teacher Essay Contest. ESSAY TOPIC: Is nationalism an asset or hindrance in today's globalized world? The winners came from Canada, Croatia, India, Indonesia, Nigeria, Russia, South Korea, the United Kingdom, and the United States. Read all the winning essays here. And the winners are: Is Nationalism an Asset or a Hindrance in Today's Globalized World? Coen Armstrong, age 16, Eton College, United Kingdom The Bane of Nations: Nationalism in the Modern World Michael Wallace, age 16, Wilton High School, United States Nationalism Stops the Movement of our Rapidly Growing Globalized World Lucy McMahon, 9th Grade Student, Miss Hall's School, Lenox MA, United States Globalization vs. Nationalism. Gross National Product vs. Gross National Happiness Oksana Kravchenko, age 21, Moscow State University of International Affairs, Russia Rekindling Nationalism through Symbolism: Asset or Hindrance to Globalism? Soumya Mahalakshmi, age 21, R. V. College of Engineering, Bengaluru, India Coexistence in the World of Nations Mirko Savković (born in Serbia now a citizen of Croatia), age 24, Cankaya University, Turkey ABOUT CARNEGIE COUNCIL Founded by Andrew Carnegie in 1914 and based in New York City, Carnegie Council for Ethics in International Affairs is an educational, nonprofit, nonpartisan organization that produces lectures, publications, and multimedia materials on the ethical challenges of living in a globalized world. For more information, go to https://www.carnegiecouncil.org.
PubMed | Institute Pasteur Paris, University of Washington, Eton College and University of Cambridge
Type: | Journal: Proceedings of the National Academy of Sciences of the United States of America | Year: 2017
Mycobacterium tuberculosis and Mycobacterium marinum are thought to exert virulence, in part, through their ability to lyse host cell membranes. The type VII secretion system ESX-1 [6-kDa early secretory antigenic target (ESAT-6) secretion system 1] is required for both virulence and host cell membrane lysis. Both activities are attributed to the pore-forming activity of the ESX-1-secreted substrate ESAT-6 because multiple studies have reported that recombinant ESAT-6 lyses eukaryotic membranes. We too find ESX-1 of M. tuberculosis and M. marinum lyses host cell membranes. However, we find that recombinant ESAT-6 does not lyse cell membranes. The lytic activity previously attributed to ESAT-6 is due to residual detergent in the preparations. We report here that ESX-1-dependent cell membrane lysis is contact dependent and accompanied by gross membrane disruptions rather than discrete pores. ESX-1-mediated lysis is also morphologically distinct from the contact-dependent lysis of other bacterial secretion systems. Our findings suggest redirection of research to understand the mechanism of ESX-1-mediated lysis.
Brodie J.,Natural History Museum in London |
Fussey G.D.,Eton College |
Wilbraham J.,Natural History Museum in London |
Guiry M.D.,National University of Ireland
Journal of Applied Phycology | Year: 2014
Specimens of a seaweed sent to Sir Joseph Banks in England at the beginning of the nineteenth century by a collector in China were described as a new species, Fucus tenax, by the English botanist and antiquarian Dawson Turner. This seaweed has been extensively used in Japan, China and Korea as a source of glue and gum and has been more recently employed in a wide range of specialised applications, including the conservation of antiquarian objects. Banks raised with Turner the possibility that similar species in Britain could be used for the extraction of ‘gelatine’. This was a very early recognition of the potential use of marine phycocolloids from seaweeds and ultimately led to a marine hydrocolloid industry with projected wholesale sales in excess of US$1.56 billion in 2014. Specimens of Fucus tenax Turner [the generitype of Gloiopeltis J. Agardh, now Gloiopeltis tenax (Turner) J. Agardh] discovered in the Natural History Museum, London (BM), and the Eton College Natural History Museum (ECNHM) are considered to be the material upon which the descriptions and illustrations published by Turner (Ann Bot 2:376–378, 1806; Typis J 2:72–134, 1808–1809) were based, and a lectotype (BM) and provisional isolectotypes (ECNHM) are designated here to facilitate future molecular studies of species of the genus. © 2014 Springer Science+Business Media Dordrecht
Smith D.A.S.,Eton College |
Gordon I.J.,International Center for Insect Physiology and Ecology |
Allen J.A.,University of Southampton
Ecological Entomology | Year: 2010
1. The aim of this paper is to investigate mechanisms of reinforcement between two semi-isolated semispecies of the African savannah butterfly Danaus chrysippus. The biogeography of colour genes suggests that four semispecies evolved in once isolated refugia. They expanded their ranges in response to Holocene climatic changes to form a hybrid zone in central-east Africa. 2. Danaus chrysippus is a superspecies within which cycles of alternating cladogenesis and reticulation among semispecies have probably operated over some 4 Myr. Semispecies are inter-fertile but show Haldane rule effects in crosses; gene flow is massive but subject to isolation by distance. 3. One semispecies shows linkage disequilibrium, vis- à-vis others, for haplotype, karyotype (W-linkage of colour genes which function as reproductive isolating barriers) and all-female broods caused by a male-killer endosymbiont. Introgression of colour genes between D. c. dorippus and D. c. chrysippus is constrained by sex linkage and male killing. 4. Reinforcement in hybrid zones comprises allochronic migration, assortative mating, (assumed) sex chromosome incompatibility and sex-ratio distortion. Gene introgression from D. c. dorippus to other semispecies is maintained by a high frequency of backcrossing between hybrid males and females of the latter. © 2010 The Royal Entomological Society.
Anderson D.E.,Eton College |
Brown E.J.,Natural England
Proceedings of the Geologists' Association | Year: 2010
Outreach arising from the study of the British Quaternary offers many benefits for society, especially because of its relevance for understanding contemporary environmental issues and environmental change. Outreach is also important for the long-term health of the academic discipline and research agenda. Through engaging with the formal education system, institutions, policy makers, planners and with the public at large, Quaternary specialists can do much to advance interest in and appreciation of the British landscape and its Quaternary record. This opinion and review article considers the importance and benefits of outreach in its many forms, makes the case for practitioners to continue and increase their involvement, offers examples of good practice, and sets out aspirations for the future. © 2009 The Geologists' Association.
Gordon I.J.,International Center for Insect Physiology and Ecology |
Ireri P.,International Center for Insect Physiology and Ecology |
Ireri P.,Kenyatta University |
Smith D.A.S.,International Center for Insect Physiology and Ecology |
Smith D.A.S.,Eton College
Biological Journal of the Linnean Society | Year: 2014
Danaus chrysippus (L.) in Africa comprises four substantially isolated semispecies that are migratory and hybridize on a seasonal basis throughout the eastern and central part of the continent. In the hybrid zone (but not elsewhere), the butterfly is commonly host to a male killing endosymbiotic bacterium, Spiroplasma sp., which principally infects one semispecies, Danaus chrysippus chrysippus in Kenya. A W-autosome mutation, inherited strictly matrilinearly, links B and C colour gene loci, which have thus gained sex-linkage in chrysippus. We have monitored variation in sex ratio and genotype at the A and C colour gene loci for two extended periods of 18 months (2004-5) and 12 months (2009-10) in adults reared from wild eggs laid on trap plants in Kasarani, near Nairobi, Kenya. Additionally, in 2009-10, all surviving adult butterflies were screened for Spiroplasma infection. The hybridizing Kasarani population is highly atypical in three respects, and has apparently been so for some 30 years: first, the sex ratio is permanently female-biased (as expected), although subject to seasonal fluctuation, being lowest (male/female) when D.c. chrysippus (cc) peaks and highest when Danaus chrysippus dorippus (CC) predominates; second, the population is invariably dominated by Cc heterozygotes of both sexes but especially females; and third, cc males are always scarce because they are systematically eliminated by male killing, whereas the CC genotype is male-biased. It is this imbalance of sex versus genotype that determines the massive departure from Hardy-Weinberg equilibrium in the population, in part because cc females have little choice but to pair with C- males. We suggest that: first, Cc hybrids of both sexes fail to disperse in the company of either parental semispecies; second, Spiroplasma positive females carrying the W-autosome mutation have a selective advantage over females that lack the translocation; third, the endoparasite and the translocation create a 'magic trait' linkage group that underlies hologenomic reproductive isolation between two emerging species, D.c. chrysippus and D.c. dorippus; and, fourth, that the predominance of males in dorippus suggests that individuals must be protected by a male-killing suppressor gene. By contrast to the C locus, Aa heterozygotes are in substantial and permanent deficit, suggesting either assortative mating between AA (chrysippus and dorippus) and aa (Danaus chrysippus alcippus), or heterozygote unfitness, or both. © 2013 The Linnean Society of London.
Lee J.,Catholic University of Korea |
Kim S.,Catholic University of Korea |
Kim J.-H.,Eton College |
Park J.,Catholic University of Korea
Journal of Nanoscience and Nanotechnology | Year: 2015
4-(10-(3',5'-diphenylbiphenyl-4-yl)anthracen-9-yl)-N,N-diphenylaniline [TATa] and a new anthracene derivative of 4-(2 or 3-tert-butyl-10-(3',5'-diphenylbiphenyl-4-yl)anthracen-9-yl)-N,N-diphenylaniline [T-TATa] isomer by introduced f-butyl group were synthesized. OLED devices of TATa and T-TATa were fabricated by solution process. Its physical properties such as optical, electrochemical, and electroluminescent properties were also investigated. Two compounds were used as emitting layer (EML) in OLED device: ITO/PEDOT (40 nm)/synthesized materials (60 nm)/TPBi (20 nm)/LiF (1 nm)/Al (200 nm). The luminance efficiency of the synthesized compounds at 10 mA/cm2 were measured 0.85 cd/A for TATa and 1.49 cd/A for T-TATa, respectively. Moreover, the power efficiency of T-TATa is 1.08 lm/W. Its value is almost two times higher than 0.56 lm/W of TATa. As a result, more improved efficiency was shown with the device in a compound including f-butyl group to TATa core part, when the deivces were prepared by solution process. © 2015 American Scientific Publishers All rights reserved.
Jenkinson C.,Eton College |
Macleod P.,Eton College
Teaching Geography | Year: 2012
The demands of the 21st century workplace require educators to develop students who are creative, ask challenging questions and are equipped with the critical thinking skills to help solve them. Games in the classroom are valuable strategies for developing these skills but the fun, variety, competition and informality that comes with playing games also help students better engage with the content. Once students have grasped the point of the game, the task can be opened up to encourage greater creativity and explore the wider complexities affecting development. This is an opportunity for them to devise their own rules, to make the game more like the process of development. Normal rules apply but they will need to think carefully about which categories they offer in order to win the other person's cards. Having played the game, the concepts can be reviewed and assessed in a variety of ways.