Natural selection: Domain, levels, and challenges

TREE vol. 8, no. 4, April

1993

warm and cool temperate rainforests, islands. and closed forests on Boundaries and mixed forests, disturbance and regeneration, mangroves, and human impact, which all conservation present important are treated as separate issues, chapters. For many Australian readers, the accounts of conflicts between foresters and environmentalists, and between the Federal and State governments, will arouse vivid memories. Adam’s admitted bias is toward flora and a botanical perspective. There is much information on the origins and history of rainforest vegetation, but beyond one short chapter (20 pages) there is little mention of the rainforest fauna. This lack is partly because biogeographic and ecological information on animals is less available than comparable data on plants. But it is also because the book does not treat the rainforest community as a biological entity. Animal-plant interactions receive little attention; there is little information on pollination and seed dispersal, even less on herbivory and nutrient cycles, and almost nothing on chemical interactions. Nor are Australian rainforests examined as habitats for animals. The biological approach to understanding still remains uncharted by authors of rainforest books. For students it would be a useful companion to more fundamental textbooks on the subject. Unfortunately, at A$170 a copy - that is 55c a page, including references and some useful indexes - it will be out of reach to most. It is puzzling that at this price no colour plates are included and that diagrams are not of a high standard. Perhaps, if the out-of-

Mechanism, Natural Selection and Historicity Natural Selection: Domains, levels, and Challenges by George C. Williams, Oxford University Press (Oxford Series in Ecology and Evolution), 1992. $45.00 hbk, $24.95 pbk (x + 208 pages) ISBN 0 79 506932 3/O 19 506933 1 George Williams has written another book. He has been an influential figure in such diverse subjects as selection, senescence, group interpretation of Fisherian reproductive value, sex ratio and sexual

for example, regarded any emergence of mind from matter as ‘magic’, and was thus led to panpsychism3. Williams believes we should keep an open mind: ‘There could be no scientific finding more important than the demonstration of a mental principle, not itself physical, but capable of altering cause-effect relations in neural machinery.’ But he makes clear that he doesn’t expect any such important finding important if true, as runs a concise review of the Bible. Williams assumes that the three principles, and no others, apply wherever life Jiro Kikkawa has arisen. Other principles, including many very useful ones (e.g. Centrefor Conservation Biology, TheUniversity mendelism, DNA replication), are of Queensland, Brisbane,Queensland 4072, secondary and of limited scope. Australia Williams classifies himself as a reductionist, despite working with ‘jars and aquariums’. References Among the many topics that 1 Rainforest Conservation Society of Williams discusses are the gene as a Queensland (1986) Tropical Rainforests unit of selection, clade selection (he of North Queensland: Their Conservation likes this subject), levels of selection, Significance, Australian Heritage optimization strategies, historicity, Commission 2 Kitching, R., ed. (1988) The Ecology of and diversity within and between Australia’s Wet Tropics, The Ecological populations. This is more a collecSociety of Australia tion of Williams’ ideas on every sub3 Webb, L.J. and Kikkawa, J., eds (1990) ject under the evolutionary sun than Australian Tropical Rainforests: a systematic treatment. But the book The Science-Values-Meaning, is no less interesting for it. Commonwealth Scientific and Industrial If there is a central theme, it is the Research Organization inadequacy of current knowledge. 4 Werren, G. and Kershaw, P., eds (1991) Although natural selection acting on The Rainforest Legacy: Australian National Rainforest Study (Vols 2 and 3), random variation is a sufficient Australian Heritage Commission explanation of evolution, Williams 5 Goudberg, N., Bonell, M. and believes we are far from having a Benzaken, D., eds (1991) Tropical complete, or even reasonably satisRainforest Research in Australia, Institute factory, knowledge of the details. In for Tropical Rainforest Studies an earlier book* he announced a cri6 Baur, G.N. (1968) The Ecological Basis sis: the prevalence of sexual reproForestry of Rainforest Management, duction in higher plants and aniCommission of New South Wales 7 Webb, L.J., Tracey, J.G. and Williams, mals is inconsistent with current W.T. (1984) Aust. J. Ecol. 9, 169-198 evolutionary theory. In this book, he expresses puzzlement over the remarkable constancy of mammalian and avian body temperatures, the electrolyte concentrations in sea vertebrates, the absence of vivipary in birds and turtles, the evolution of senescence, the inflexiLike its predereproduction. bility of sex determination, and cessors’**, this book is thoughtful, several others. The most difficult of provocative and pleasantly idiosynall, he says, is stasis; the various cratic. Unlike them, it deals with a examples of stasis ‘form the most variety of subjects rather than conserious set of difficulties facing centrating on a single theme. evolutionary theory today’. To me, The book begins with a ‘philowhat he calls a desperation hypothsophical position’ in which Williams esis - normalizing clade selection says that biological research has seems not at all desperate, nor does three principles: mechanism (as normalizing selection in general, in opposed to vitalism), natural selecview of nature’s love for mediocrity tion (trial and error, as opposed to a and the large genetic variance even rational plan), and historicity (recogin static species. But for me to say nition of historical contingency). that it doesn’t seem mysterious is Today’s vitalism is found in not to say we understand the mind-body dualism. Sewall Wright, details. place cartoon strips, silhouettes of some interesting exotic animals, but not essential black-and-white photographs and reproductions of advertisements had been dispensed with, space could have been saved and costs reduced. In its treatment of the unique Australian rainforest and in its accounts of botanical and human history, as well, of course, as the spelling of ‘rainforest’, this book is thoroughly Australian and establishes a new genre. That is to be applauded.

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One of his challenges and anomalies is ‘Haldane’s dilemma’, the cost of natural selection. In his famous article4, Haldane said, ‘In the paper I shall try to make quantitative the fairly obvious statement that natural selection cannot occur with great intensity for a number of characters at once’. He showed that the amount of excess reproduction required to effect a gene substitution is a simple decreasing function of its initial frequency. If evolution consists mainly of substituting initially rare mutations, the cost can indeed be large. But if the process is mainly one of shifting frequencies of relatively common alleles, the cost is much less, and with quasi-truncation selection may be very much less. I should like to suggest that Haldane’s other famous principle, the mutation load5, may turn out to be more of a dilemma than the cost of natural selection. Drosophila experiments suggest that deleterious mutations occur at a rate of one or more per gamete6. If this is true and generalizable, the mutation load

is enormous unless natural selection contrives to pick off several mutations at once. This indeed happens with rank-order selection, which is expected if selection is soft. But it can’t happen without recombination, so we have one more (perhaps the most important) reason for the maintenance of sexual reproduction - the problem that Williams found so perplexing a few years ago. It is typical of ecological books to ignore much of what genetical theory has to offer, just as it is typical of genetics books to ignore ecology. In this regard Williams’ discussion is on the ecological side. Molecular evolution and mathematical theory get short shrift and Kimura is nowhere mentioned. I don’t criticize this, for an author is entitled to choose his own subject. Yet, if there is a great deal of neutral DNA - and there is - there must also be very weakly selected DNA. This is the stuff of darwinian gradualism, and in this respect Kimura has strengthened Darwin (if he needed it). For me, an exciting prospect in the near

future, as evolution becomes more experimental and makes increasing use of molecular and mathematical knowledge, is the imminent rapprochement of molecular and organismic evolution. At the moment the processes and their discussants are marching to different drummers, but they are beginning to shew signs of responding to the same beat.

to combine work on the conservation of both biological organisms and the human cultures which inhabit the forests. Several chapters demonstrate that local peoples, both tribal and peasant cultures, are already involved in the fight to conserve their lands. Case studies from the Chimane conservation programme in Bolivia, the Cuyabeno Wildlife Reserve in Ecuador and the Amuesha Indians in Peru are all good examples of the involvement in both conservation and sustainable land use of indigenous peoples. Many chapters also deal with the local folk societies, variously termed ribereiios, campesinos or caboclos. The knowledge of these peoples about the forest and of its management has often been overlooked. Here we see clearly that these often neglected people have much to contribute to the issues of wise resource management. The emphasis on caboclos/ribererSo societies is the most significant new contribution of this volume. Good examples of the management systems of these people are given from the upper Amazon village of Santa Rosa in Peru, the tidal floodplain dwellers of the Amazon estuary at Combu in

Par& Brazil and the extractivists in both Guatemala and Acre, Brazil. The approach of most authors is realistic and does not try to romanticize the ‘noble savage’ of Rousseau. The local peoples have already caused considerable disturbance to neotropical forests but, on the whole, their practices do not diminish the biological diversity. However, the Ache of Paraguay destroy bee hives to obtain honey, cut down fruiting trees to gather the fruit and wipe out entire troops of monkeys, while the local riberetio societies described tend to overhunt and overfish. In spite of the difficulties, we cannot hope to strike a correct balance between conservation and sustainable use until we have learned from the experience of millenia of indigenous peoples and of several centuries from folk cultures. A fascinating account of the different types of agriculture among the ribereiios of Peru by author and editor Padoch shows that these people use eight different types of agricultural systems. The Amazon delta system described by Anderson is both sustainable and lucrative, owing to the special circumstances of that region.

James F. Crow GeneticsDept.Universityof Wisconsin, Madison,WI 53706,USA References 1 Williams, G.C. (1966) Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought, Princeton University Press 2 Williams, G.C. (1975) Sex and Evolution, Princeton University Press 3 Wright, S. (1964) Monist 48,265290 4 Haldane, J.B.S. (1957) J. Genet. 55, 51 l-524 5 Haldane, J.B.S. (1937) Am. Nat. 71, 337-349 6 Crow, J.F. (1992) Curr. Biol. 2,605-607

Tropical Forests and Peoples Conservation of Neotropical Forests: Working from Traditional Resource Use edited by Kent H. Redford and Christine Columbia Padoch, University Press, 1992. $52.00 hbk (475 pages) ISBN 0 23107602 9 In recent years, conservation has come to mean a lot more than simply the preservation of endangered species in biological reserves. The 1980 World Conservation strategy’, its 1991 revision* and the Brundtland report3 have all stressed the need for a balance between conservation and sustainable use of natural ecosystems. This constructive trend towards a balanced approach to conservation was also the focus of the 1992 United Nations Conference on Environment and Development (UNCED), held in Rio de Janeiro. It is significant that indigenous peoples were present in Rio and that the preservation of forest peoples and their culture was also debated. This timely book brings together well an interdisciplinary team of authors from biological, sociological and anthropological backgrounds. The only realistic way to slow down the destruction of tropical forests is 152