hooics -- .- Vertebrate Form and

TREE vol. 1, no. 6, December 1986

Function

Functional Vertebrate Morphology

edited by Milton Hildebrand, Dennis M. Bramble, Karel F. Liem and David B. Wake, Harvard University Press, 1985. f29.75 (430 pages) LSBN 0 674 32775 6

Looking at Vertebrates: A Practical Guide to Vertebrate Adsptations

by Elizabeth Rogers, Longman, 1986. f9.95 (xi f 195 pages) ISBN 0582 45086 1

Since the 187Os, when the first evolu- tionary series of fossil horses were proposed by Kovalevsky and by Marsh, vertebrates have played a major role in historical evolutionary studies. This partly derives from a natural interest in the organisms most similar to ourselves, but also reflects the potentially high informa- tion content of the vertebrate skeleton. But how to make use of it? Every fossil skeleton mutely de- mands to be fleshed out, to have a lifestyle assigned to it. Every series of related vertebrates tantalizes us with the prospect of turning it into a story about adaptation to different environments. Speculative compari- sons with living animals are very easy to propose but are of limited value. However, the form of the vertebrate skeleton is an expression of the mode of action and function of the musculo-skeletal system, and this must bear some relationship, possibly compromised, to the living animal’s adaptation to its environ- ment. The student of vertebrate evolution must therefore turn to the functional morphologist who can make testable observations on living organisms. However, only in the last two decades have students of verte- brate functional morphology been able to exploit the possibilities for analytical study offered by living animals.

Functional morphology used to be based on scholarly interpretation of still photographs, the shapes of joints, and the assumed mode of action of a few prominent muscles. The last 20 years have seen it revolu- tionized by the application of tech- nology. High-speed photography illuminated by light and X-rays has provided insights into the real move- ments that animals make when feed- ing, breathing or moving, while elec- tromyological studies demonstrate the precise muscle-firing sequences that implement these movements. The now massive film archives of vertebrate behaviour, both in the field and in the laboratory, document a behavioural diversity which match-

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es the morphological diversity. We now have the potential to know what vertebrates really do and how their morphology permits them to do it.

The volume by Hildebrand et a/. is an overview of the state of the art in this area. It is divided into 18 separ- ately authored chapters: one on general principles, one on scaling effects and support, seven on differ- ent modes of locomotion, two on energetics and respiration, three on feeding systems, three on receptors and neural control and one overview of current morphological practice. It is targeted at vertebrate biologists in the broadest sense, with the particu- lar goal of keeping lecturers and ad- vanced students in touch with what functional morphologists are doing and why. As a vertebrate palaeon- tologist on the periphery of such work, I was astounded at how dated my view had become in those areas which I had not consciously attempt- ed to ‘keep up with’. The topics have been expanded or condensed to fit a relatively standard chapter size, thus giving a generous 20 pages to the study of digging quadrupeds (Hil- debrand) which is at an early de- scriptive phase, but a very general- ized 18-page overview of the mech- anics of - swimming vertebrates (Webb and Blake) which can barelv touch on specific groups or anatom: ical features.

The book is well written but pre- supposes interest within the student reader, interest which must come from earlier, more basic priming in the subject. Rogers’ book is a practi- cal class textbook aimed at first year undergraduates and upper school students. It is part of the recent trend to give general vertebrate texts a functional instead of a developmen- tal and phylogenetic emphasis. As many of us have found, this makes morphology more accessible to a wider range of students. In this book, one can see functional information filtering down through the education system, although it is very much in the form of received information rather than methodology. Questions for students are inserted throughout the text, but many can only be answered by ‘looking it up’ either with ease or with difficulty. However, the text is very clear, and most of the illustrations are of good quality. It is a book of our times in that it assumes that the class organizer may have limited resources and the illustra- tions emphasize specimens of im- portant but less readily available vertebrate types. It is divided into eight rather large chapters reflecting, I suspect, eight one-day practical classes, and would have been more

flexible to use had the information been divided into a greater number of smaller modules.

By writing textbooks like these to lead different levels of students into the subject, the authors have in- vested their time well on behalf of their discipline. There is little point in carrying out research unless you also ensure that the next generation is motivated to pick up where you leave off. But what is the next gener- ation of functional morphologists going to pick up? Where is functional morphology going and why is it of relevance to the student of evolu- tion?

As discussed in Liem and Wake’s closing chapter of Hildebrand et a/., most morphologists work on the assumption that adaptation is opti- mal in relation to the environment and that evolutionary changes in adaptation represent pure optimiz- ation. Structural, functional, be- havioural and ecological analyses can be carried out on this assump- tion, and many of the chapters in Hildebrand et al. are written on this basis. But although vast numbers of superb empirical observations are being generated by this side of func- tional morphology, there is an ele- ment of tautology underlying this approach. If everything is perfectly adapted, what control do we have to assess adaptation against? Are there no limitations or compromises to be recognized? Liem and Wake point out that for the evolutionary bio- logist the more valuable view of adaptation is that it represents the optimization of body form and func- tion within the constraints laid down by development and evolutionary history. The long-term task is to integrate functional morphology, systematics and developmental studies into coherent testable mod- els of the evolution of a given group, and for this school of thought the structural and functional analyses are just the beginning. They must then be turned into a history of trans- formation of designs by placing them on an independently con- structed phylogenetic scheme based on character distribution. This per- mits an analysis of the sequence of acquisition of characteristics, recog- nition of the innovations which trig- ger evolutionary diversification and those which do not, or alternatively, recognition of the constraints which inhibit diversification and those which do not. Experimental demon- stration of developmental par- ameters and constraints in related living forms can then be applied to some of the resulting structural pat- terns. All variation in structure is

TREE vol. 1, no. 6, December 1986

produced by differences in patterns el of the evolutionary pathways of of growth and these can be observed even one group of vertebrates repre- and interfered with to demonstrate sents an immense challenge, but the possibilities and limitations of a gives a renewed sense of direction to given structural system. several branches of zoology. Only by

To bring these several disciplines integrating them can we hope to together to produce a coherent mod- build up a view of historical evolu-

tion which is based on potentially falsifiable hypotheses rather than reasonable speculation.

Andrew Milner Depaltment of Biology. Birkbeck College, Malet Street,

London WClE 7HX. UK.

Ecology, Recreation and Tourism

by John M. Edington and M. Ann Edington, Cambridge University Press, 1986. f25.~0/$39.50 hbl;, f9.95&15.95 pbk (viii f 200 pages) ISBN 0 52131409 7

That humans are an ecological factor to be reckoned with is a fact well- known to anyone involved with assessment of the environmental effects of construction projects or pollution. That people can also upset natural systems when they are hav- ing fun is a facet of ecology which has perhaps not received the atten- tion it deserves.

Some people actually enjoy killing things and effectively enter eco- systems as predators; the role of predators in natural systems is reas- onably well understood, so the effects of hunters can be modelled and in some cases controlled by land managers. More peaceful souls may simply lie about on beaches or walk the countryside, and some seek the enjoyment of birdwatching and simi- lar pursuits. The effects of non- aggressive recreation vary from the obvious - colonial seabirds tend to desert if their colonies are disturbed by rock-climbers-to the very subtle, as illustrated by the beautiful eco- logical studies of Box Hill in southern England’; here detailed assessments have been made of localized vegeta- tional changes arising from tramp- ling and from soil enrichment by the activities of picnicking visitors.

Humans in the 198Os, armed with the technology of modern re- creational gadgets and with foreign exchange differentials inducing them to extend their recreation into far-flung parts, can insinuate them- selves into many an ecosystem. Snowmobilers collapse vole-runs and scuba divers kick slow-growing fan corals. Both of these are acciden- tal destructive acts which, if allowed

to take place on a large enough scale, will ultimately modify food chains, trophic structure, animal be- haviour and many other aspects of the systems.

The degree to which land mana- gers can influence the effects of re- creation on their particular piece of ground depends upon their motiva- tion for doing so, as well as on their ability to restrict the activities of visi- tors. The curtailing of other people’s recreation must be balanced with the revenue it brings. Many nature re- serves and national parks are finan- cially dependent upon people who come to observe, trample and dis- turb. So the control is generally more of a damage limitation exercise based upon trying to keep people off the most sensitive bits than a genuine attempt to reconcile the visi- tors ecologically. Enlightened mana- gers, or those with more spending power, may be able to provide ‘honeypot’ attractions which lure visitors to the more resilient areas, but ecologically the effect is much the same as that of a fence.

The first half of the Edingtons’ book is essentially a catalogue of some of the interactions between people having fun and the natural systems in which they are having it. The authors dip for their examples into the waters off California where, we are told, whales can become separated from their offspring by the boats of whale-watchers; into the African Parks where safari hotels can be built on stilts to minimize disturb- ance to game; into the Great Barrier Reef where the Marine Park Author- ity have managed to zone the Park according to the degree of disturb- ance to which it should be subjected. In addition, there is much material from the British Isles. It is perhaps surprising, however, that there is no mention of the skiing developments in the Scottish Highlands, and little discussion of the progress that has been made throughout the world in

establishing marine nature reserves in which recreational activities of divers and fishermen are controlled.

In the second half of the book the ecosphere strikes back, and the au- thors investigate biological hazards which face people on holiday. Sand- flies, sharks and jellyfish all get a mention and there are some handy tips on how to keep bears off your lunch. A chapter on disease illus- trates the extent to which tourism has brought millions more people into areas where they are likely to contract diseases which they would probably never have heard of if they had stayed at home. But there is no mention of the threat to isolated human and primate communities posed by tourists bringing in viruses.

The final chapter introduces the ecological problems engendered by the back-up facilities demanded by modern tourists: construction of hotels, pollution and road building. After all, one man’s fun is another man’s business.

A book of this length cannot hope to discuss all of the ecological im- plications of recreation and tourism, and nor does it try. Neither can it provide much in the way of detailed predictive information to facilitate planning of tourist and recreational facilities in areas of environmental importance, as every case has its own unique set of problems and con- straints. What it does is to provide a set of case histories, and with a refer- ence list of heroic proportions it is a useful source of background material for anyone with an interest in man’s role in the natural world.

Stephen Warman

Nature Conservancy Council, Trelissick, Feock, Truro, Cornwall, UK.

Reference 1 Streeter, D.T. (1971) in The Scientific Management ofAnimal and Plant Communities for Conservation (Duffey, E. and Watt, A.S., eds), pp. 459-468, Blackwell

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