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Eton, United Kingdom

Gordon I.J.,ICIPE | Edmunds M.,University of Central Lancashire | EDgar J.A.,CSIRO | Lawrence J.,Stellenbosch University | And 2 more authors.
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. Source

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. Source

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 Source

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. Source

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. Source

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