- Email: [email protected]
Stay with Darwin
CORRESPONDENCE
Symmetry and sexual selection
References Brookes, M. and Pomiankowski, A. (1994) Trends Ecol. Evol. 9, 201-202 Watson, P.J. and Thornhill,R. (1994) Trends Ecol. Evol. 9, 21-25 Mflller, A.P. and Pomiankowski, A. (1993) Genetica 89,267-279 Oakes, E.J. and Barnard, P. Anim. Behav. (in press) Thomas, A.L.R. (1993) Proc. R. Sot. London Ser. i3 254,181-189 Jennions,M.D. (1993) Trends Ecol.Evol.8,241-243 Dennett, DC (1991) Consciousness Explained, Penguin Balmford, A. and Read, A.F. (1991) Trends Ecol. Evol. 6, 274-276
In their recent TREE news & comment, Brookes and Pomiankowskii reviewed studies of female choice based on the symmetry of male characters. They noted that female preferences based on trait symmetry have been conclusively shown in barn swallows (Hirundo rustica) where apparent tail symmetry was altered using Tipp-Ex, and in zebra finches (Jaeniopygia guttata) where symmetry in coloured leg bands was manipulated. There are two issues we wish to highlight. First, there is a tendency to exaggerate the evidence for female choice of symmetric ornaments. Brookes and Pomiankowski cite two reviews*,3 as further evidence that females prefer symmetric traits. However, these reviews only cover one other experimental manipulation of symmetry. Ironically, Oakes and Barnard4 actually found a female preference for asymmetry in an aviary experiment with paradise whydahs (Vidua paradisaea). The ‘additional evidence’ that mating success correlates with symmetry is largely inconclusive. There is strong natural selection for symmetry in many traits5, so asymmetric males may be handicapped in terms of foraging efficiency, success in male-male competition and predator avoidance. As Brookes and Pomiankowski note, all of these factors are likely to reduce male mating success independently of direct female choice for symmetric secondary sexual characters. Second, there is good evidence that symmetry is sometimes an indicator of genetic quality2,3. However, it need not follow from this that a female preference for symmetry has evolved because of its relationship with genetic quality5.6. There is likely to be a general sensory bias in most animals for symmetry. important features of the biotic environment such as predators, prey and conspecifics are symmetric while plants (with the exception of flowers) and geological features are not (see Ref. 7). In zebra finches, for example, there has obviously not been selection in the wild for a female preference for symmetric leg rings. Moreover, leg ring symmetry is unrelated to genetic quality. Why then do females possess a preference for symmetrically arranged leg rings? One can argue that the female preference results from a generalization of a preference for symmetry which evolved because of ‘good gene’ processes. However, it could equally be a by-product of a preference that arose in another context. This is really just a restatement of the claim that Fisherian, good gene and sensory exploitation processes may eventually all culminate in female preferences for male traits that are indicators of male genetic qualitya. Only if increased symmetry is always associated with males of superior genetic quality do ‘by-product’ explanations of preferences for symmetry become invalid.
Jennions and Oakes are right when they say that there are few convincing experimental studies of mate preference for symmetry - that is why we wrote our News & Commentl. But they are wrong to promote Oakes and Barnard’s* experiment on paradise whydahs as a good study. This experiment suffers from a simple design flaw. It is fallacious to conclude that female preference in the paradise whydah is for asymmetric males. Oakes and Barnard manipulated the two longest tail feathers of male paradise whydahs. Asymmetric tails were created by lengthening one and shortening the other and symmetric controls had the same length for both feathers. The average tail feather length in asymmetric and symmetric birds was the same. Surprisingly, females preferred to sit near asymmetric males rather than symmetric controls in partitioned aviaries. Superficially it looks as if females prefer asymmetry. But it is equally plausible to suppose that females pick the male with the longest apparent tail length which is the ‘asymmetric’ male. This second interpretation is credible because preference for long tails has been experimentally demonstrated in other whydah species3,4. Another difficulty is that males were held in small cages in which they could perch but not fly about. This would have limited discrimination if females assess tail feathers during flight. The lack of proper experimental design precludes any conclusions being made from this study. In contrast, the papers we reported have unambiguous designs. Mtiller’s5.6 experiments on barn swallows manipulated both asymmetry and tail length independently, showing that both were important in mate choice. Likewise, Swaddle and Cuthill’s experiments on zebra finches were specifically designed to remove any confounding effects of changes in trait size with asymmetry. In these two studies, the conclusion that females prefer symmetric ornaments can be made with confidence.
Michael D. Jennions Edward J. Oakes
Martin Brookes Andrew Pomiankowski
Dept of Zoology, University of Oxford, South Parks Road, Oxford, UK OX1 3PS
Dept of Genetics and Biometry, University College London, 4 Stephenson-Way, London, UK NW1 2HE
440
Reply from M. Brookes and A. Pomiankowski
References Brookes, M. and Pomiankowski, A. (1994) Trends Ecol. Evol. 9, 201-202 Oakes, E.J. and Barnard, P. Anim. Behav. (in press) Andersson, M. (1982) Nature 299,818-820 Andersson, S. (1992) Anim. Behav. 43,379-388 MBller, A.P. (1992) Nature 357, 238-240 M@ller,A.P. (1993) Behav. Ecol. Sociobiol. 32, 371-376 Swaddle, J.P. and Cuthill, I.C. (1994) Nature 367, 165-166
Stay with Darwin Short1 describes his experience with teaching evolutionary biology to medical students. I applaud his approach, but believe this can now be done much more elegantly, by joining ‘the darwinian revolution’, which is on the verge of entering several new areas of medicine. During 1991, the evolutionary biologist George C. Williams and the psychiatrist Randolph M. Nesse reviewed works in different fields relevant for medicine by applying the adaptationist programme*. Instead of asking mainstream medical questions like ‘how does the body function’, they ask the complementary question ‘why does the body function the way it does’. The focus is on how traits of the body may have given our ancestors advantages in their daily struggle for survival and/or reproduction, that is, how the body adapted to a Stone-Age way of life. In the dawn of darwinian medicine, Williams and Nesse highlight four relevant areas: (1) Infections should be interpreted as an escalating ‘arms-race’ between the pathogens and their hosts, with the host trying to resist the attacks of the pathogens, while the pathogens try to resist the host’s resistance. (2) Injuries and toxins -toxins exist in several plant species as a defence against herbivores. To counter this defence, we may have developed mechanisms like allergy to expel potentially harmful toxins from the body. (3) Genetic diseases and ageing when viewing some diseases and undesirable processes where the culprit genes seem to have been recognized, always check whether the genes may have been beneficial early in life (as may be the case with ageing). (4) Unnatural environments - due to rapid cultural evolution, we have created novel environments which humans have never before experienced. From a genetic standpoint, humans living today are Stone-Age hunter-gatherers displaced through time to a world that differs from that for which our genetic constitution was selecteds. Recent meetings of the researchers who use principles from darwinism to guide their research have presented us with novel, though controversial hypotheses about themes in physiology and medicine as viewed through ‘evolutionary lenses’. Menstruation is hypothesized to be a defense against sperm-borne pathogens*, but the hypothesis was recently severely criticized (6.1. Strassman, unpublished). There seems to be a genetic conflict between a mother and her foetus as to the amount (beyond necessary) of nutrients that should be transferred*. The first book concerning infections in a darwinian perspective has already appeared4. TREE vol.
9, no.
II November
1994
CORRESPONDENCE Several interesting sessions about ‘darwinian medicine’ were held in Michigan in June (6th Annual Meeting of the Human Behavior and Evolution Society), and a book that probably will become a modern classic will be released next Januarys. Adaptive thinking is also providing insight into psychiat@, as well as in psychology7,8, in explaining the mindg. When teaching students to cope with humans and future living conditions on earth in the years to come, we will have several reasons to stay with Darwin and his theories.
Iver Mysterud Division of Zoology, Dept of Biology, University of Oslo, Box 1050 Blindern, N-0316 Oslo, Norway
References Short, R.V. (1994) Trends Ecol. Evol. 9, 275 Westoby, M. (1994) Trends Ecol. Evol. 9,1-2
Eaton, S.B., Konner. M. and Shostak. M. (1988) Am. J. Med. 84.739-749 Ewald, P.W. (1993) Evolution of Infectrous Disease, Oxford UniversityPress
Nesse, R.M. and Williams, G.C. Makrng Sense of Sickness: Medicine,
The Darwinian
Revolution
Comes to
Times Books (in press) Wenegrat, 6. (1990) Sociobiological Psychiatry: A New Conceptual Framework, LexingtonPress Crawford, C.B., Smith, M. and Krebs, D., eds (1987) Sociobiology and Psychology: Ideas, issues and Applications, Lawrence Erlbaum Badcock, C. (1993) PsychoDarwinism: The New Synthesis
religion into the classroom, something many of US resist doing. But when the topic of evolution is on the table, religion is too, in our students’ minds, whether we are willing to admit it or not. By addressing it directly, we prevent students from being able to compartmentalize these two parts of their lives (and thus from passing Short’s examinations without fundamentally altering their own beliefs). Introducing these ideas works best in a discussion format. I have found discussion to be effectively stimulated by a Nova film called ‘God, Darwin and Dinosaurs’, which presents a detailed picture of the scientific creationists’ challenge to evolution while clearly supporting the scientific point of view. Another helpful resource I require students to read is Douglas Futuyma’s Science on Trial* (especially the first chapter). Both the film and the book raise an important issue: the distinction between scientific beliefs and religious beliefs. Every biology (and medical) student ought to be able to define what characterizes a scientific belief (its basis in physical evidence, its falsifiability, etc.). Medical students in particular need to be able to distinguish scientific claims from bogus ones, so this issue gives the discussion additional importance. I am indebted to Craig Nelson for first stimulating me to think about bringing religion into my evolution courses, and for suggestions on how to do so effectively. I recommend his article ‘Creation, evolution, or both? A multiple model approach’ in Robert Hanson’s edited volume3.
Paulette Bienychudek
of Darwin and Freud,
Harper Collins Barkow, J., Cosmides, L. and Tooby, J., eds (1992) The Adapted Mind: Evolutionary
Lewis and Clark College, Portland, OR 97219, USA
Psychology
References
and the Generation
of Culture,
Oxford University Press
R.V. Short, in ‘Darwin, have I failed you?’ laments his inability to instill in medical students a belief in evolutionl. In the final paragraph, Short asks ‘why had I failed in my efforts to teach the concept [evolution] to my students?’ In over 10 years of teaching evolutionary biology to American undergraduates, I have gradually decided that teaching biological principles is not sufficient. Because resistance to evolutionary beliefs is usually based on the existence of deeply rooted conflicting religious beliefs, it is essential to confront these beliefs head-on. The religious right (in Australia, I imagine, just as in the US) has been very effective in convincing large numbers of people that there is an inherent conflict between belief in a Supreme Being and belief in the process of evolution. Students so convinced who believe in the existence of a god are forced to disbelieve in evolution in order to avoid eternal punishment. It is our job as educators to counter these propaganda efforts and to help our students to see that there is no inherent conflict. Because beliefs in god and in evolution represent entirely different levels of explanation, they are in fact quite compatible. One way to illustrate this is to provide students with information about the many religions that oppose the teaching of ‘creation science’ in state-supported schools. This perforce brings TREE
vol.
9, no.
high operated by the Rothamsted Insect Survey’. The enzyme E4 confers cross resistance to organophosphate, carbamate and pyrethroid insecticides, and the highly resistant strains of M. persicae now found in the field In the UK show elevated E4 levels, associated in strains R, and R, with gene amplification and autosomal translocation. The elevated esterases may be detected in individual insects electrophoretically or by immunoassay, while the strains displaying gene amplification may be identified using a specific DNA probes-6. The suction-trap data are being used to investigate the spatio-temporal dynamics of resistance in this species7. To preserve E4 activity in M. persicae, the live alatae (winged forms) are trapped in a solution (solution 21), of 25% glycerol containing Triton X-100 detergent (O.S%), 100mM KCI, 20mM Tris(hydroxymethyl)aminomethane to maintain pH at 9.0, 1mM oxytetracycline (antibiotic agent) and 1uM CuSO, (antimycotic agent)8. Using this solution, E4 activity levels are maintained for up to 15 days even at 30°C Plant viruses can also be Identified in therr aphid vectors after storage In ‘solution 21’. This has enabled assessment of virus risk based on suction trap samples to take account of the potential infectivity of vectors7. Clearly, the solution has potential for preservation of other enzymes, biomolecules and viruses, especially in situations where frozen storage for purposes of preservation is not possible, although the copper sulphate would have to be replaced by another antimycotic agent for monitoring the activity of enzymes that are inhibited by Cu*+ ions.
II
November
1994
Short, R.V. (1994) Trends Ecol. fvol. 9, 275 Futuyma, D. (1983) Science on Trial: The Case for Evolution, Pantheon Nelson, C. (1986) in Science and Creation: Geological, Theological and Educational Perspectives (Hanson, R., ed.), pp. 128-159,
Macmillan
Another solution for preserving activity and integrity?
Hugh D. Loxdale Cliff P. Brookes Ian P. Woiwod Richard Harrington Dept of Entomology and Nematology, Rothamsted Experimental Station, Harpenden, Herts, UK AL5 2JQ References 1 Taylor, D.J., Finston, T.L. and Hebert. P.D.N. (1994) Trends Ecol. Evol. 9, 230 2 Taylor, L.R. (1986) J. Anim. Ecol. 55, l-38 3 Devonshire, A.L. (1989) in Nectrophoretic Studies on Agricultural Pests (Loxdale. H.D. and den Hollander, J., eds), pp. 363-374, Clarendon Press Devonshire, A.L. and Field, L.M. (1991) Annu. Rev. Ent. 36, l-23
Field, L.M. and Devonshire, A.L. (1992) in We were most interested to read the recent letter by Taylor et al.1 in which they describe methods for successfully preserving enzyme activity and DNA integrity from Daphnia pulex, Drosophila melanogaster and goldfish (Carassius auratus) by air drying tissues in 15% trehalose. The problem of storage of biomolecules is particularly important in ecological studies where samples are collected away from laboratories or, as in our case, using automatic sampling devices that are emptied daily or less frequently. For our entomological studies at Rothamsted, we need to preserve the esterase-4 (E4) activity of the peach-potato aphid (Myzus persicae), a major pest species in this country, captured in the nationwide network of suction traps 12.2 m
Resistance ‘91: Achievements and Developments in Combating insecticide Resistance (Denholm. I., Devonshire, A.L. and
Hollomon, D.W., eds), pp. 240-250, Elsevier Loxdale, H.D. (1994) In The Identifrcatfon Characterization
and
of Pest Organisms
(Hawksworth, D.L.. ed.), pp. 337-375, CAB international Tatchell, G.M. (1993) Sugar Beet Research and Education
Committee
Paper 2691
Tatchell, G.M.. Thorn, M., Loxdale. H.D. and Devonshire, A.L. (1988) in Proceedings of Brighton Crop Protection Conference (Pests and Diseases) 4C-15, pp. 4399444, British Crop
Protection Council
441
Symmetry and sexual selection
References Brookes, M. and Pomiankowski, A. (1994) Trends Ecol. Evol. 9, 201-202 Watson, P.J. and Thornhill,R. (1994) Trends Ecol. Evol. 9, 21-25 Mflller, A.P. and Pomiankowski, A. (1993) Genetica 89,267-279 Oakes, E.J. and Barnard, P. Anim. Behav. (in press) Thomas, A.L.R. (1993) Proc. R. Sot. London Ser. i3 254,181-189 Jennions,M.D. (1993) Trends Ecol.Evol.8,241-243 Dennett, DC (1991) Consciousness Explained, Penguin Balmford, A. and Read, A.F. (1991) Trends Ecol. Evol. 6, 274-276
In their recent TREE news & comment, Brookes and Pomiankowskii reviewed studies of female choice based on the symmetry of male characters. They noted that female preferences based on trait symmetry have been conclusively shown in barn swallows (Hirundo rustica) where apparent tail symmetry was altered using Tipp-Ex, and in zebra finches (Jaeniopygia guttata) where symmetry in coloured leg bands was manipulated. There are two issues we wish to highlight. First, there is a tendency to exaggerate the evidence for female choice of symmetric ornaments. Brookes and Pomiankowski cite two reviews*,3 as further evidence that females prefer symmetric traits. However, these reviews only cover one other experimental manipulation of symmetry. Ironically, Oakes and Barnard4 actually found a female preference for asymmetry in an aviary experiment with paradise whydahs (Vidua paradisaea). The ‘additional evidence’ that mating success correlates with symmetry is largely inconclusive. There is strong natural selection for symmetry in many traits5, so asymmetric males may be handicapped in terms of foraging efficiency, success in male-male competition and predator avoidance. As Brookes and Pomiankowski note, all of these factors are likely to reduce male mating success independently of direct female choice for symmetric secondary sexual characters. Second, there is good evidence that symmetry is sometimes an indicator of genetic quality2,3. However, it need not follow from this that a female preference for symmetry has evolved because of its relationship with genetic quality5.6. There is likely to be a general sensory bias in most animals for symmetry. important features of the biotic environment such as predators, prey and conspecifics are symmetric while plants (with the exception of flowers) and geological features are not (see Ref. 7). In zebra finches, for example, there has obviously not been selection in the wild for a female preference for symmetric leg rings. Moreover, leg ring symmetry is unrelated to genetic quality. Why then do females possess a preference for symmetrically arranged leg rings? One can argue that the female preference results from a generalization of a preference for symmetry which evolved because of ‘good gene’ processes. However, it could equally be a by-product of a preference that arose in another context. This is really just a restatement of the claim that Fisherian, good gene and sensory exploitation processes may eventually all culminate in female preferences for male traits that are indicators of male genetic qualitya. Only if increased symmetry is always associated with males of superior genetic quality do ‘by-product’ explanations of preferences for symmetry become invalid.
Jennions and Oakes are right when they say that there are few convincing experimental studies of mate preference for symmetry - that is why we wrote our News & Commentl. But they are wrong to promote Oakes and Barnard’s* experiment on paradise whydahs as a good study. This experiment suffers from a simple design flaw. It is fallacious to conclude that female preference in the paradise whydah is for asymmetric males. Oakes and Barnard manipulated the two longest tail feathers of male paradise whydahs. Asymmetric tails were created by lengthening one and shortening the other and symmetric controls had the same length for both feathers. The average tail feather length in asymmetric and symmetric birds was the same. Surprisingly, females preferred to sit near asymmetric males rather than symmetric controls in partitioned aviaries. Superficially it looks as if females prefer asymmetry. But it is equally plausible to suppose that females pick the male with the longest apparent tail length which is the ‘asymmetric’ male. This second interpretation is credible because preference for long tails has been experimentally demonstrated in other whydah species3,4. Another difficulty is that males were held in small cages in which they could perch but not fly about. This would have limited discrimination if females assess tail feathers during flight. The lack of proper experimental design precludes any conclusions being made from this study. In contrast, the papers we reported have unambiguous designs. Mtiller’s5.6 experiments on barn swallows manipulated both asymmetry and tail length independently, showing that both were important in mate choice. Likewise, Swaddle and Cuthill’s experiments on zebra finches were specifically designed to remove any confounding effects of changes in trait size with asymmetry. In these two studies, the conclusion that females prefer symmetric ornaments can be made with confidence.
Michael D. Jennions Edward J. Oakes
Martin Brookes Andrew Pomiankowski
Dept of Zoology, University of Oxford, South Parks Road, Oxford, UK OX1 3PS
Dept of Genetics and Biometry, University College London, 4 Stephenson-Way, London, UK NW1 2HE
440
Reply from M. Brookes and A. Pomiankowski
References Brookes, M. and Pomiankowski, A. (1994) Trends Ecol. Evol. 9, 201-202 Oakes, E.J. and Barnard, P. Anim. Behav. (in press) Andersson, M. (1982) Nature 299,818-820 Andersson, S. (1992) Anim. Behav. 43,379-388 MBller, A.P. (1992) Nature 357, 238-240 M@ller,A.P. (1993) Behav. Ecol. Sociobiol. 32, 371-376 Swaddle, J.P. and Cuthill, I.C. (1994) Nature 367, 165-166
Stay with Darwin Short1 describes his experience with teaching evolutionary biology to medical students. I applaud his approach, but believe this can now be done much more elegantly, by joining ‘the darwinian revolution’, which is on the verge of entering several new areas of medicine. During 1991, the evolutionary biologist George C. Williams and the psychiatrist Randolph M. Nesse reviewed works in different fields relevant for medicine by applying the adaptationist programme*. Instead of asking mainstream medical questions like ‘how does the body function’, they ask the complementary question ‘why does the body function the way it does’. The focus is on how traits of the body may have given our ancestors advantages in their daily struggle for survival and/or reproduction, that is, how the body adapted to a Stone-Age way of life. In the dawn of darwinian medicine, Williams and Nesse highlight four relevant areas: (1) Infections should be interpreted as an escalating ‘arms-race’ between the pathogens and their hosts, with the host trying to resist the attacks of the pathogens, while the pathogens try to resist the host’s resistance. (2) Injuries and toxins -toxins exist in several plant species as a defence against herbivores. To counter this defence, we may have developed mechanisms like allergy to expel potentially harmful toxins from the body. (3) Genetic diseases and ageing when viewing some diseases and undesirable processes where the culprit genes seem to have been recognized, always check whether the genes may have been beneficial early in life (as may be the case with ageing). (4) Unnatural environments - due to rapid cultural evolution, we have created novel environments which humans have never before experienced. From a genetic standpoint, humans living today are Stone-Age hunter-gatherers displaced through time to a world that differs from that for which our genetic constitution was selecteds. Recent meetings of the researchers who use principles from darwinism to guide their research have presented us with novel, though controversial hypotheses about themes in physiology and medicine as viewed through ‘evolutionary lenses’. Menstruation is hypothesized to be a defense against sperm-borne pathogens*, but the hypothesis was recently severely criticized (6.1. Strassman, unpublished). There seems to be a genetic conflict between a mother and her foetus as to the amount (beyond necessary) of nutrients that should be transferred*. The first book concerning infections in a darwinian perspective has already appeared4. TREE vol.
9, no.
II November
1994
CORRESPONDENCE Several interesting sessions about ‘darwinian medicine’ were held in Michigan in June (6th Annual Meeting of the Human Behavior and Evolution Society), and a book that probably will become a modern classic will be released next Januarys. Adaptive thinking is also providing insight into psychiat@, as well as in psychology7,8, in explaining the mindg. When teaching students to cope with humans and future living conditions on earth in the years to come, we will have several reasons to stay with Darwin and his theories.
Iver Mysterud Division of Zoology, Dept of Biology, University of Oslo, Box 1050 Blindern, N-0316 Oslo, Norway
References Short, R.V. (1994) Trends Ecol. Evol. 9, 275 Westoby, M. (1994) Trends Ecol. Evol. 9,1-2
Eaton, S.B., Konner. M. and Shostak. M. (1988) Am. J. Med. 84.739-749 Ewald, P.W. (1993) Evolution of Infectrous Disease, Oxford UniversityPress
Nesse, R.M. and Williams, G.C. Makrng Sense of Sickness: Medicine,
The Darwinian
Revolution
Comes to
Times Books (in press) Wenegrat, 6. (1990) Sociobiological Psychiatry: A New Conceptual Framework, LexingtonPress Crawford, C.B., Smith, M. and Krebs, D., eds (1987) Sociobiology and Psychology: Ideas, issues and Applications, Lawrence Erlbaum Badcock, C. (1993) PsychoDarwinism: The New Synthesis
religion into the classroom, something many of US resist doing. But when the topic of evolution is on the table, religion is too, in our students’ minds, whether we are willing to admit it or not. By addressing it directly, we prevent students from being able to compartmentalize these two parts of their lives (and thus from passing Short’s examinations without fundamentally altering their own beliefs). Introducing these ideas works best in a discussion format. I have found discussion to be effectively stimulated by a Nova film called ‘God, Darwin and Dinosaurs’, which presents a detailed picture of the scientific creationists’ challenge to evolution while clearly supporting the scientific point of view. Another helpful resource I require students to read is Douglas Futuyma’s Science on Trial* (especially the first chapter). Both the film and the book raise an important issue: the distinction between scientific beliefs and religious beliefs. Every biology (and medical) student ought to be able to define what characterizes a scientific belief (its basis in physical evidence, its falsifiability, etc.). Medical students in particular need to be able to distinguish scientific claims from bogus ones, so this issue gives the discussion additional importance. I am indebted to Craig Nelson for first stimulating me to think about bringing religion into my evolution courses, and for suggestions on how to do so effectively. I recommend his article ‘Creation, evolution, or both? A multiple model approach’ in Robert Hanson’s edited volume3.
Paulette Bienychudek
of Darwin and Freud,
Harper Collins Barkow, J., Cosmides, L. and Tooby, J., eds (1992) The Adapted Mind: Evolutionary
Lewis and Clark College, Portland, OR 97219, USA
Psychology
References
and the Generation
of Culture,
Oxford University Press
R.V. Short, in ‘Darwin, have I failed you?’ laments his inability to instill in medical students a belief in evolutionl. In the final paragraph, Short asks ‘why had I failed in my efforts to teach the concept [evolution] to my students?’ In over 10 years of teaching evolutionary biology to American undergraduates, I have gradually decided that teaching biological principles is not sufficient. Because resistance to evolutionary beliefs is usually based on the existence of deeply rooted conflicting religious beliefs, it is essential to confront these beliefs head-on. The religious right (in Australia, I imagine, just as in the US) has been very effective in convincing large numbers of people that there is an inherent conflict between belief in a Supreme Being and belief in the process of evolution. Students so convinced who believe in the existence of a god are forced to disbelieve in evolution in order to avoid eternal punishment. It is our job as educators to counter these propaganda efforts and to help our students to see that there is no inherent conflict. Because beliefs in god and in evolution represent entirely different levels of explanation, they are in fact quite compatible. One way to illustrate this is to provide students with information about the many religions that oppose the teaching of ‘creation science’ in state-supported schools. This perforce brings TREE
vol.
9, no.
high operated by the Rothamsted Insect Survey’. The enzyme E4 confers cross resistance to organophosphate, carbamate and pyrethroid insecticides, and the highly resistant strains of M. persicae now found in the field In the UK show elevated E4 levels, associated in strains R, and R, with gene amplification and autosomal translocation. The elevated esterases may be detected in individual insects electrophoretically or by immunoassay, while the strains displaying gene amplification may be identified using a specific DNA probes-6. The suction-trap data are being used to investigate the spatio-temporal dynamics of resistance in this species7. To preserve E4 activity in M. persicae, the live alatae (winged forms) are trapped in a solution (solution 21), of 25% glycerol containing Triton X-100 detergent (O.S%), 100mM KCI, 20mM Tris(hydroxymethyl)aminomethane to maintain pH at 9.0, 1mM oxytetracycline (antibiotic agent) and 1uM CuSO, (antimycotic agent)8. Using this solution, E4 activity levels are maintained for up to 15 days even at 30°C Plant viruses can also be Identified in therr aphid vectors after storage In ‘solution 21’. This has enabled assessment of virus risk based on suction trap samples to take account of the potential infectivity of vectors7. Clearly, the solution has potential for preservation of other enzymes, biomolecules and viruses, especially in situations where frozen storage for purposes of preservation is not possible, although the copper sulphate would have to be replaced by another antimycotic agent for monitoring the activity of enzymes that are inhibited by Cu*+ ions.
II
November
1994
Short, R.V. (1994) Trends Ecol. fvol. 9, 275 Futuyma, D. (1983) Science on Trial: The Case for Evolution, Pantheon Nelson, C. (1986) in Science and Creation: Geological, Theological and Educational Perspectives (Hanson, R., ed.), pp. 128-159,
Macmillan
Another solution for preserving activity and integrity?
Hugh D. Loxdale Cliff P. Brookes Ian P. Woiwod Richard Harrington Dept of Entomology and Nematology, Rothamsted Experimental Station, Harpenden, Herts, UK AL5 2JQ References 1 Taylor, D.J., Finston, T.L. and Hebert. P.D.N. (1994) Trends Ecol. Evol. 9, 230 2 Taylor, L.R. (1986) J. Anim. Ecol. 55, l-38 3 Devonshire, A.L. (1989) in Nectrophoretic Studies on Agricultural Pests (Loxdale. H.D. and den Hollander, J., eds), pp. 363-374, Clarendon Press Devonshire, A.L. and Field, L.M. (1991) Annu. Rev. Ent. 36, l-23
Field, L.M. and Devonshire, A.L. (1992) in We were most interested to read the recent letter by Taylor et al.1 in which they describe methods for successfully preserving enzyme activity and DNA integrity from Daphnia pulex, Drosophila melanogaster and goldfish (Carassius auratus) by air drying tissues in 15% trehalose. The problem of storage of biomolecules is particularly important in ecological studies where samples are collected away from laboratories or, as in our case, using automatic sampling devices that are emptied daily or less frequently. For our entomological studies at Rothamsted, we need to preserve the esterase-4 (E4) activity of the peach-potato aphid (Myzus persicae), a major pest species in this country, captured in the nationwide network of suction traps 12.2 m
Resistance ‘91: Achievements and Developments in Combating insecticide Resistance (Denholm. I., Devonshire, A.L. and
Hollomon, D.W., eds), pp. 240-250, Elsevier Loxdale, H.D. (1994) In The Identifrcatfon Characterization
and
of Pest Organisms
(Hawksworth, D.L.. ed.), pp. 337-375, CAB international Tatchell, G.M. (1993) Sugar Beet Research and Education
Committee
Paper 2691
Tatchell, G.M.. Thorn, M., Loxdale. H.D. and Devonshire, A.L. (1988) in Proceedings of Brighton Crop Protection Conference (Pests and Diseases) 4C-15, pp. 4399444, British Crop
Protection Council
441