- Email: [email protected]
Swinging safari
212
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exhortation from his influential 1974 book, The Genetic Basis of Evolutionary Change1, that population genetics ‘always begins with the characterization of the genetic variation in populations’. My discomfort is that the study of genetic basis seems to have become divorced from its justification, evolutionary change. Lewontin, characteristically, suggested in the preface to his book that he had posed the wrong question: ‘…the question was not simply, How much genetic variation is there?…but rather, How much genetic variation is there that can be the basis of adaptive evolution?’ Answers to this question are conspicuously absent from the present volume. The differences between current population genetics, exemplified by this book, versus 1974 are striking. Molecular data have enabled rich tests of the neutral theory, and allowed the genealogical history of haplotypes to be inferred. Most of the chapters are brief pithy reviews of these and other aspects of the maintenance of genetic variation within populations. Charlesworth and Hughes, on the maintenance of genetic variance in life-history traits, is a fine example. One pleasure of such a wide-ranging volume is becoming aware of generalizations outside one’s own area of interest, such as the importance of gene conversion in generating molecular variation. All of this is good; population geneticists can think well of their field, its place in biology, their illustrious intellectual ancestors and themselves. Ask any other sort of biologist about population genetics, however, and they probably have no idea about these developments. More troubling is that, even when these nuggets are fully explained, one is more likely to get a shrug than a hug from the lucky learner. I believe that this is because the group of population geneticists represented here has, by and large, not pursued questions relevant to the process of adaptation. A bitter confirmation of this view is Lewontin’s statement in this book that ‘population genetics is a science of methodologies’. The intellectually fascinating review of codon bias by Kreitman and Antezana is a case in point. Codon bias has provided us with the first probable example of the nearly neutral theory in action. It is feasible to investigate because the data are so abundant that subtle patterns can
TRENDS in Ecology & Evolution Vol.16 No.4 April 2001
be detected and interpreted. Allow me to respectfully but dialectically suggest, however, that most biologists do not give a damn about codon bias, precisely because it forms no part of the variation that can be the basis of adaptive evolution. More typically, Frankham’s list of the major questions in evolutionary quantitative genetics includes several aspects of the maintenance of variation, but nothing about the uses to which that variation might be put. Chapters on the measurement of natural selection (Christiansen and Prout, Arnason and Barker) do address evolutionary process directly, but reveal the embarrassing detail that such measurements are apparently never carried out any more. How many times must we cite Christiansen and Frydenberg2 before someone actually reapplies the technique? Hickey’s sensible chapter on the evolution of sex, and Coyne and Orr’s typically datarich view of speciation represent exceptions in that they take real evolutionary phenomena as their subjects. They represent the noble tradition of sticking to a general question, and bringing whatever evidence can be mustered to bear on it. Followers of Lewontin, myself included, have been uncritical in our acceptance of the notion that if we only knew how much genetic variation existed, and why, we would understand something important about the potential for adaptation. How little this central tenet has been examined is indicated by the fact that Lande, in his almost Biblical explication of quantitative genetics, finds that Dobzhansky3 is the best citation to the idea that among and within species variation are of the same kind. Taken at face value, our three canonical theories of the maintenance of genetic variation each suggest otherwise. Neutrality implies irrelevance of variation to the problem rather than relevance. Mutation–selection balance implies that much of the observed variation is unconditionally deleterious and never of use for adaptation. Balancing selection implies that polymorphic systems will at least be resistant to novel selection pressures. These are not fatal objections to these theories, as we are all familiar with the genotype–environment interactions and epistasis that can be invoked to coax adaptation from such variation. There is, however, an alternative hypothesis, and
that is that the process of adaptation is mutation limited4,5, rather than variation limited. Only the study of the products and process of adaptation can resolve this dilemma, and such efforts do proceed6. It is a shame that the followers of Lewontin have so little to do with these efforts. References 1 Lewontin, R.C. (1974). The Genetic Basis of Evolutionary Change, Columbia 2 Christiansen, F.B. and Frydenberg, O. (1976). Selection component analysis of natural polymorphisms using mother-offspring samples of successive cohorts. In Population Genetics and Ecology (Karlin, S. and Nevo, E., eds), pp. 277–301. Academic Press 3 Dobzhansky, T. (1951). Genetics and the Origin of Species (3rd edn), Columbia University Press 4 Paquin, C.E. and Adams, J. (1983) Relative fitness can decrease in evolving asexual populations of S. cerevisiae. Nature 306, 368–371 5 Elena, S.F. et al. (1996) Punctuated evolution caused by selection of rare beneficial mutations. Science 272, 1802–1804 6 Kopp, A. et al. (2000) Genetic control and evolution of sexually dimorphic characters in Drosophila. Nature 408, 553–559
David Houle Dept of Biological Science, Florida State University, Tallahassee, FL 32306-1100, USA. e-mail: [email protected]
Swinging safari Wildlife Conservation by Sustainable Use edited by Herbert H.T. Prins, Jan Geu Grootenhuis and Thomas T. Dolan Kluwer Academic Press, 2000. £115.00 (xiv + 496 pages) ISBN 0 412 79730 5
This book addresses the important question of how wildlife outside protected areas in Africa can be conserved in the face of relentless human pressure to expand agriculture. The cultural, political and economic background to this question is fraught. The colonial era saw the authorities seize land and wildlife, organize them to suit European economic interests and distinguish areas for hunting, National Parks, ranches and those remaining for subsistence African
http://tree.trends.com 0169–5347/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved.
Forum
agriculture. The wildlife of Africa became something to be preserved by and for Europeans. To cap it all, Western economic policies, together with local economic mismanagement of the sort common in Western agriculture (distortion of agricultural production through subsidies, dismal attempts to improve farmers’ incomes through misguided ‘development’) have had some catastrophic effects. Witness, for example, the imposition by the European Union of veterinary cordon fences across migration paths of wild ungulates in Botswana, resulting in terrible losses. The editors have assembled an impressive band of people with deep personal experience of wildlife management and of trying to resolve the conflicts between forms of land and resource use. They have compiled a massive and detailed body of work with the main aim of showing how wildlife can be conserved because it makes economic sense to do so. Only when the economic value of wildlife can be realized, through tourism, trophy hunting (i.e. armed tourism) and by direct use in the traditional manner, can it then take its place as a sustainable form of land use equal or superior to agriculture or ranching. Numerous case studies in the book emphasize this. The final chapter reveals that ‘an exciting new concept is emerging in Africa; stakeholders in wildlife utilization as a form of sustainable land use decide themselves which form of wildlife use is best’. Re-emergence of an old concept, one might think. Elsewhere, without apparent irony, ‘The conclusion drawn is that community-based
TRENDS in Ecology & Evolution Vol.16 No.4 April 2001
approaches that allow local people access to and control over wildlife resources may have more positive impacts on conservation and sustainable use than those strategies that dispossess local people and reduce their access to wildlife resources’. Isn’t this where we started? There have, indeed, been some striking successes in assisting local communities to exploit wildlife – notable CAMPFIRE (Communal Areas Management Programme for Indigenous Resources), which originated in Rhodesia in the 1960s. Trophy hunting earns big money, and some local communities have funded development in the form of clinics and schools through this source of revenue. Clearly, this is an incentive to maintain viable wildlife populations. Resource-poor communities, or those dumped on overcrowded Communal Areas have few such opportunities, and it can be observed that edible and inedible wildlife has long since disappeared from such places. The reoccupation of protected areas and ranchland occurring in some parts of Africa will probably result in a similar fate for the wildlife there. For example, the Save Valley Conservancy in southeast Zimbabwe, home to globally threatened species such as the African Wild Dog, has been recently forcibly resettled by landhungry peasants. That land tenure is the central issue affecting the future of wildlife is reinforced starkly by the many chapters devoted to wildlife ranching. Amalgamation of unprofitable beef units into jointly managed safari and ecotourism operations makes good economic and conservation sense, but is harder to achieve outside the extensive
213
private sector land holdings of colonial origin. Nevertheless, this model is increasingly being put into practice in areas under African communal management where the human population density is low enough to permit it. The book contains useful chapters on wildlife as reservoirs of diseases of livestock, on the impacts of wildlife on agriculture, and on livestock–wildlife competition. It is unfortunate that the book does not give much impression of how Africans of non-European origin perceive the problem, aside from one chapter on traditional relations with wildlife contributed by an (American) anthropologist. The contributors are almost all European, at least by descent. Inevitably, therefore, these admirable and thorough analyses are contributions from a somewhat alien cultural perspective. In saying this, I do not intend to question the sincerity or integrity of the editors and authors in their examination of the options for wildlife conservation. They have produced a book that is a rich information source and that will have lasting value. It will certainly inform similar debates in the many other parts of the world where the same dilemmas arise. But I do wonder what the average savanna-dweller makes of it all. Andrew Illius Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Rd, Edinburgh, UK EH9 3JT. e-mail: [email protected]
Corrigendum In the February issue of Trends in Ecology and Evolution, the reference for the Journal Club article by Ken Wilson (The costs of resistance in Drosophila: blood cells count, Ken Wilson, 2001 Trends. Ecol. Evol. 16, 72–73) should have read: Kraaijveld, L. et al. (2001) Basis of trade-off between parasitoid resistance and larval competitive ability in Drosophila melanogaster. Proc. R. Soc. London B Biol. Sci. 268, 259–261. We apologize to readers for this correction. PII: S0169-5347(01)02120
Erratum In the Book Review by Steve Jones (Sex differences. Developmental and Evolutionary Strategies, by Linda Mealey, 2001 Trends Ecol. Evol. 16, 56) the number of pages in the book was given incorrectly. It should read 480 not 1480 pages. We apologize to readers for this error. PII: S0169-5347(01)02136-X
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exhortation from his influential 1974 book, The Genetic Basis of Evolutionary Change1, that population genetics ‘always begins with the characterization of the genetic variation in populations’. My discomfort is that the study of genetic basis seems to have become divorced from its justification, evolutionary change. Lewontin, characteristically, suggested in the preface to his book that he had posed the wrong question: ‘…the question was not simply, How much genetic variation is there?…but rather, How much genetic variation is there that can be the basis of adaptive evolution?’ Answers to this question are conspicuously absent from the present volume. The differences between current population genetics, exemplified by this book, versus 1974 are striking. Molecular data have enabled rich tests of the neutral theory, and allowed the genealogical history of haplotypes to be inferred. Most of the chapters are brief pithy reviews of these and other aspects of the maintenance of genetic variation within populations. Charlesworth and Hughes, on the maintenance of genetic variance in life-history traits, is a fine example. One pleasure of such a wide-ranging volume is becoming aware of generalizations outside one’s own area of interest, such as the importance of gene conversion in generating molecular variation. All of this is good; population geneticists can think well of their field, its place in biology, their illustrious intellectual ancestors and themselves. Ask any other sort of biologist about population genetics, however, and they probably have no idea about these developments. More troubling is that, even when these nuggets are fully explained, one is more likely to get a shrug than a hug from the lucky learner. I believe that this is because the group of population geneticists represented here has, by and large, not pursued questions relevant to the process of adaptation. A bitter confirmation of this view is Lewontin’s statement in this book that ‘population genetics is a science of methodologies’. The intellectually fascinating review of codon bias by Kreitman and Antezana is a case in point. Codon bias has provided us with the first probable example of the nearly neutral theory in action. It is feasible to investigate because the data are so abundant that subtle patterns can
TRENDS in Ecology & Evolution Vol.16 No.4 April 2001
be detected and interpreted. Allow me to respectfully but dialectically suggest, however, that most biologists do not give a damn about codon bias, precisely because it forms no part of the variation that can be the basis of adaptive evolution. More typically, Frankham’s list of the major questions in evolutionary quantitative genetics includes several aspects of the maintenance of variation, but nothing about the uses to which that variation might be put. Chapters on the measurement of natural selection (Christiansen and Prout, Arnason and Barker) do address evolutionary process directly, but reveal the embarrassing detail that such measurements are apparently never carried out any more. How many times must we cite Christiansen and Frydenberg2 before someone actually reapplies the technique? Hickey’s sensible chapter on the evolution of sex, and Coyne and Orr’s typically datarich view of speciation represent exceptions in that they take real evolutionary phenomena as their subjects. They represent the noble tradition of sticking to a general question, and bringing whatever evidence can be mustered to bear on it. Followers of Lewontin, myself included, have been uncritical in our acceptance of the notion that if we only knew how much genetic variation existed, and why, we would understand something important about the potential for adaptation. How little this central tenet has been examined is indicated by the fact that Lande, in his almost Biblical explication of quantitative genetics, finds that Dobzhansky3 is the best citation to the idea that among and within species variation are of the same kind. Taken at face value, our three canonical theories of the maintenance of genetic variation each suggest otherwise. Neutrality implies irrelevance of variation to the problem rather than relevance. Mutation–selection balance implies that much of the observed variation is unconditionally deleterious and never of use for adaptation. Balancing selection implies that polymorphic systems will at least be resistant to novel selection pressures. These are not fatal objections to these theories, as we are all familiar with the genotype–environment interactions and epistasis that can be invoked to coax adaptation from such variation. There is, however, an alternative hypothesis, and
that is that the process of adaptation is mutation limited4,5, rather than variation limited. Only the study of the products and process of adaptation can resolve this dilemma, and such efforts do proceed6. It is a shame that the followers of Lewontin have so little to do with these efforts. References 1 Lewontin, R.C. (1974). The Genetic Basis of Evolutionary Change, Columbia 2 Christiansen, F.B. and Frydenberg, O. (1976). Selection component analysis of natural polymorphisms using mother-offspring samples of successive cohorts. In Population Genetics and Ecology (Karlin, S. and Nevo, E., eds), pp. 277–301. Academic Press 3 Dobzhansky, T. (1951). Genetics and the Origin of Species (3rd edn), Columbia University Press 4 Paquin, C.E. and Adams, J. (1983) Relative fitness can decrease in evolving asexual populations of S. cerevisiae. Nature 306, 368–371 5 Elena, S.F. et al. (1996) Punctuated evolution caused by selection of rare beneficial mutations. Science 272, 1802–1804 6 Kopp, A. et al. (2000) Genetic control and evolution of sexually dimorphic characters in Drosophila. Nature 408, 553–559
David Houle Dept of Biological Science, Florida State University, Tallahassee, FL 32306-1100, USA. e-mail: [email protected]
Swinging safari Wildlife Conservation by Sustainable Use edited by Herbert H.T. Prins, Jan Geu Grootenhuis and Thomas T. Dolan Kluwer Academic Press, 2000. £115.00 (xiv + 496 pages) ISBN 0 412 79730 5
This book addresses the important question of how wildlife outside protected areas in Africa can be conserved in the face of relentless human pressure to expand agriculture. The cultural, political and economic background to this question is fraught. The colonial era saw the authorities seize land and wildlife, organize them to suit European economic interests and distinguish areas for hunting, National Parks, ranches and those remaining for subsistence African
http://tree.trends.com 0169–5347/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved.
Forum
agriculture. The wildlife of Africa became something to be preserved by and for Europeans. To cap it all, Western economic policies, together with local economic mismanagement of the sort common in Western agriculture (distortion of agricultural production through subsidies, dismal attempts to improve farmers’ incomes through misguided ‘development’) have had some catastrophic effects. Witness, for example, the imposition by the European Union of veterinary cordon fences across migration paths of wild ungulates in Botswana, resulting in terrible losses. The editors have assembled an impressive band of people with deep personal experience of wildlife management and of trying to resolve the conflicts between forms of land and resource use. They have compiled a massive and detailed body of work with the main aim of showing how wildlife can be conserved because it makes economic sense to do so. Only when the economic value of wildlife can be realized, through tourism, trophy hunting (i.e. armed tourism) and by direct use in the traditional manner, can it then take its place as a sustainable form of land use equal or superior to agriculture or ranching. Numerous case studies in the book emphasize this. The final chapter reveals that ‘an exciting new concept is emerging in Africa; stakeholders in wildlife utilization as a form of sustainable land use decide themselves which form of wildlife use is best’. Re-emergence of an old concept, one might think. Elsewhere, without apparent irony, ‘The conclusion drawn is that community-based
TRENDS in Ecology & Evolution Vol.16 No.4 April 2001
approaches that allow local people access to and control over wildlife resources may have more positive impacts on conservation and sustainable use than those strategies that dispossess local people and reduce their access to wildlife resources’. Isn’t this where we started? There have, indeed, been some striking successes in assisting local communities to exploit wildlife – notable CAMPFIRE (Communal Areas Management Programme for Indigenous Resources), which originated in Rhodesia in the 1960s. Trophy hunting earns big money, and some local communities have funded development in the form of clinics and schools through this source of revenue. Clearly, this is an incentive to maintain viable wildlife populations. Resource-poor communities, or those dumped on overcrowded Communal Areas have few such opportunities, and it can be observed that edible and inedible wildlife has long since disappeared from such places. The reoccupation of protected areas and ranchland occurring in some parts of Africa will probably result in a similar fate for the wildlife there. For example, the Save Valley Conservancy in southeast Zimbabwe, home to globally threatened species such as the African Wild Dog, has been recently forcibly resettled by landhungry peasants. That land tenure is the central issue affecting the future of wildlife is reinforced starkly by the many chapters devoted to wildlife ranching. Amalgamation of unprofitable beef units into jointly managed safari and ecotourism operations makes good economic and conservation sense, but is harder to achieve outside the extensive
213
private sector land holdings of colonial origin. Nevertheless, this model is increasingly being put into practice in areas under African communal management where the human population density is low enough to permit it. The book contains useful chapters on wildlife as reservoirs of diseases of livestock, on the impacts of wildlife on agriculture, and on livestock–wildlife competition. It is unfortunate that the book does not give much impression of how Africans of non-European origin perceive the problem, aside from one chapter on traditional relations with wildlife contributed by an (American) anthropologist. The contributors are almost all European, at least by descent. Inevitably, therefore, these admirable and thorough analyses are contributions from a somewhat alien cultural perspective. In saying this, I do not intend to question the sincerity or integrity of the editors and authors in their examination of the options for wildlife conservation. They have produced a book that is a rich information source and that will have lasting value. It will certainly inform similar debates in the many other parts of the world where the same dilemmas arise. But I do wonder what the average savanna-dweller makes of it all. Andrew Illius Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Rd, Edinburgh, UK EH9 3JT. e-mail: [email protected]
Corrigendum In the February issue of Trends in Ecology and Evolution, the reference for the Journal Club article by Ken Wilson (The costs of resistance in Drosophila: blood cells count, Ken Wilson, 2001 Trends. Ecol. Evol. 16, 72–73) should have read: Kraaijveld, L. et al. (2001) Basis of trade-off between parasitoid resistance and larval competitive ability in Drosophila melanogaster. Proc. R. Soc. London B Biol. Sci. 268, 259–261. We apologize to readers for this correction. PII: S0169-5347(01)02120
Erratum In the Book Review by Steve Jones (Sex differences. Developmental and Evolutionary Strategies, by Linda Mealey, 2001 Trends Ecol. Evol. 16, 56) the number of pages in the book was given incorrectly. It should read 480 not 1480 pages. We apologize to readers for this error. PII: S0169-5347(01)02136-X
http://tree.trends.com