ASBS Newsletter – Book Review
An Introduction to Plant Taxonomy – Second edition
written by Charles Jeffrey (1)
Plant Taxonomy and Biosystematics – Second edition
written by Clive A. Stace (2)
(From: ASBS Newsletter Number 70, March 1992)
(1) Publisher: Cambridge University Press, Cambridge. 1982. x+154 pp. ISBN 0-521-28775-8.
During most of this century, taxonomy has been on the decline from its pre-eminent position in the biology of the previous two centuries. This has been true both for the public perception of its importance within biology (since it now has to compete with genetics, physiology and ecology for attention) and also for its role in undergraduate teaching in universities (where it has deteriorated to being little more than a plant identification subject). This decline is global in scale, although it has been particularly prevalent in Great Britain and the United States of America; and Australia has clearly tended to follow the same line.
In many ways, the decline can be considered to have slowed in recent decades, because of the injection of new ideas (such as phenetics and cladistics) and new techniques (such as in multivariate analysis, cytogenetics, and reproductive biology). In fact, there is even the possibility that it may be feasible to stop the decline completely, given the recent enthusiasm for the study of molecular genetics and the current craze for the conservation of biodiversity.
Unfortunately, just when things were looking better, institutional belt-tightening in the northern hemisphere has been going on at an unprecedented rate, and taxonomists have joined the dole queue en masse. Four factors are often proferred as being involved in the current situation:- an increased rate of attrition among taxonomists caused by retirement without recruitment; lack of systematic teaching at undergraduate level and reduced opportunities at postgraduate level; research funding methods and priorities that disadvantage taxonomy; and the perception that taxonomy is only justifiable if it involves molecular systematics. Australia has not yet reached the same parlous state, but history should tell us that it cannot be far away; and recent governmental changes in higher education are not promising.
It therefore seems to be important that systematics regains its place as the discipline that unites all of the other areas of biology. This central role stems from the fact that systematics makes use of data provided by all of the other biological disciplines, as well as providing the phylogenetic framework within which these data are interpreted. Indeed, as an undergraduate student one of the first things that impressed me about plant taxonomists was the sheer breadth of their knowledge compared to other botanists, as well as their understanding of plant relationships. Systematics thus has the potential to greatly improve its current position, provided active measures are taken to achieve this.
In order to regain this lost position, two things must therefore change:- the public perception of taxonomy; and the undergraduate teaching of it. The public perception can only change by active persuasion on the part of taxonomists. This applies particularly to raising the public profile of the discipline and in emphasizing its valuable role in modern society, but it also applies to changing the perception of systematics within schools. The undergraduate teaching can only change by presenting systematics as a modern scientific study of intrinsic and practical interest in its own right, rather than as merely an aid to identification.
The traditional perception of taxonomy is of a subjective and intuitive study, characterized most elegantly by the comment that "a good taxonomy is what a good taxonomist thinks it is". Unfortunately, this image does not go down well in the modern technological age, and physicists and chemists are by-and-large correct when they dismiss this sentiment as being characteristic of an art rather than of a science. Systematics must be perceived as a science that can hold its own in the current information era, rather than as an old-fashioned stamp-collecting exercise; and this perception must be presented to both the general public as well as to university undergraduates in all areas of biology.
With this background in mind, I thought that it might be a useful exercise to look at the current crop of books aimed at giving an understanding of plant taxonomy to the rest of the world, to see how they meet this challenge. The first two books are reviewed here, and the others will be covered in later issues of the Newsletter.
The book by Charles Jeffrey is the most basic of the books, being intended as a simple introduction to the subject for non-scientists (teachers, horticulturalists, and naturalists), other biologists, and students up to the level of first-year undergraduates. This aim is the book's greatest asset and also its greatest weakness. The book assumes nothing more than the most general knowledge of botany, and it is therefore eminently readable by the general public; but in attempting to distill the essence of taxonomy it's the science that gets short shrift. Consequently, taxonomy comes across as a somewhat boring and unexciting exercise to just those people who should be encouraged to think otherwise.
This de-emphasis on science is in spite of the fact that Jeffrey invokes the "scientific method" as a point in favour of using "natural classifications" for "scientific purposes". I'm not sure what "method" he is referring to, but since he comments wryly that "it is still hypotheses that phylogenies remain", he is clearly not enamoured of the hypothetico-deductive methods used extensively by scientists in other disciplines. This old-fashioned view of science is a strong bias in the book. Unfortunately, Jeffrey also specifically excludes "the investigation of the evolutionary bases of our knowledge of the plant world" from his view of taxonomy, even suggesting that this area has been "over-emphasized" in other books. He prefers, instead, to concentrate on the "classical core of plant taxonomy". Anyone reading this book will thus quickly conjure up the traditional image of taxonomists poring conscientiously over their stamp albums.
The book is a revised edition of one first published in 1968, and is organized into 8 chapters, plus 3 appendices. The publication quality is high, with very few errors; and there is a useful balance of original illustrations and tables. The index is good, given the intended audience; and the writing style is commendably simple. Most concepts are explained as plainly as possible, with straightforward examples, most of which involve British plants or at least objects familiar to the British public.
The first chapter is Introducing Classification, a brief (5 pages) but somewhat misleading (because it is exclusively classical) overview of why taxonomy exists. Chapter 2 covers the Fundamentals of Classification, this being a good and commendably brief (7 pages) account of why classification is possible in the biological world. The Process of Classification (chapter 3) is a somewhat longer (24 pages) but rather simplistic coverage of how a taxonomist works and what data they are looking for, concentrating very much on the usefulness of barriers to breeding - if only it really was this simple in practice!
Chapter 4 should be the heart of this book, as it covers The Taxonomic Hierarchy and its Meaning. This is a fairly detailed (27 pages) but somewhat misleading (because overly simplistic) discussion of natural and artificial classifications, and how they relate to our actual classifications. Unfortunately, Jeffrey defines natural classifications as those that group together "objects that are most alike in most ways", and thus concludes that phenetic and cladistic groupings (for example) should be perfectly congruent - this is almost never true in practice, and is unlikely in theory either. Given his definition, it is almost impossible that a natural classification could ever exist in reality. Other simplifications include ignoring the difficulties of finding defining characters for natural groups due to the inevitable exceptions, and drawing straight lines on graphs that "in no way imply linear relationships". He also concludes that groupings above the level of the species are not objective, but are a matter of "informed and considered opinion of experienced and competent taxonomists", which claim should make any scientist cringe, while at the same time noting that there are "some principles which must be followed", none of which is of any practical value.
Chapter 5 is a good coverage of The Scientific Naming of Plants, as would be expected form the author of Biological Nomenclature (1977). However, the 40 pages are far too detailed for an introductory text, even covering the minutiae of cultivated plants. The Practical Naming of Plants (chapter 6) is a good coverage of the various means of identifying plants, although its 14 pages only cover dichotomous keys and comparison with herbarium specimens, and the families that the readers are suggested to learn to recognize are all very British. Chapter 7, Systems of Classification, is a brief (9 pages) and therefore limited account of the history of classification, the only modern systems presented being those of Bentham & Hooker, Engler, and Takhtajan. The final chapter, Taxonomy our Contemporary, is a poor (4 pages) attempt to make taxonomy sound useful in the modern world.
The first appendix is a good discussion of the types of morphological data that have proven to be of use in taxonomy, and it contains a useful introduction to the more practical aspects of the work. Appendix B is a list of books recommended for further reading and reference, but it is heavily weighted towards European audiences. The final appendix is an outline of a classification of plants, with some attempt to equate the groups with more traditional common names.
All in all, this is a somewhat flawed attempt to introduce taxonomy to a wider audience. Its concentration on classical taxonomy, and its over-simplification of taxonomic practice, leave the reader with a rather old-fashioned view of modern systematics. Science and taxonomy shall never be mixed in this view. The book could be markedly improved by reducing chapter 5 and using the space gained to increase the scientific content of chapter 4. This would move the emphasis from the minutiae of naming (as it is in the present book) to the science of classification (as it needs to be in a successful exposition).
The book by Clive Stace is intended to be an introductory text for university biology undergraduates, although its introductory nature would make it readable by other scientists and by serious amateurs. The stated aim is to present systematics as an exciting contemporary science; and there is the conscious perception that most of the people to whom taxonomy is taught will in fact not become taxonomists, so that what they therefore need is an understanding of the aims, principles and methods rather than just an exposition of the boring facts. However, the book definitely assumes a knowledge of first-year undergraduate biology or the equivalent.
The book is a revised edition of one first published in 1980, which was very well received, being reprinted in 1984 and 1985. It is organized into 10 chapters in 3 sections (The Basis of Taxonomy; Sources of Taxonomic Information; Taxonomy in Practice), plus an appendix. The publication quality is high, with very few errors; and there is a useful collection of reproduced and original illustrations The index is fairly comprehensive, including the generic names cited; and the writing style is also straightforward. The order of the chapters is more logical than that of the book by Jeffrey, and the examples are more wide-ranging (even eucalypts get a mention) although Europe predominates.
The first chapter covers The Scope of Taxonomy, a fairly brief (12 pages) account of classifications and their various roles. Unfortunately, this doesn't really make any clear statement of what taxonomy is (the definition of "classification" is unusable), or how it qualifies as a science. Chapter 2 describes The Development of Plant Taxonomy, a lengthy (47 pages) exposition of the various phases through which systematics has passed. This chapter also describes the techniques for data collection and analysis used in each phase; and so phenetics and cladistics are described and evaluated in this section, which makes them appear as historical curiosities rather than as modern developments. This arrangement resulted in a number of critical comments on the first edition of the book, and this new edition has not alleviated the problem to any great extent.
The next five chapters cover the types of data used by taxonomists. Chapter 3 is a good coverage of Structural Information (17 pages), including morphology and anatomy, while chapter 4 covers Chemical Information (23 pages). Protein and DNA sequencing are included here, but are not as clearly explained as are secondary metabolites, and they are given very little coverage considering their current trendiness. Chromosomal Information is discussed in far too much detail in chapter 5 (20 pages), including incidentals of number, structure and behaviour. Chapter 6 covers Information from Breeding Systems (27 pages), also in unnecessary detail in places; while Chapter 7 is a generally good discussion of Information from Plant Geography and Ecology (22 pages).
Chapter 8 concerns The Process of Classification, a comparatively brief (14 pages) account of the practical aspects of taxonomic characters and the taxonomic hierarchy, which still comes across as a bit of an art. Chapter 9, Ways and Means (23 pages), is a fairly traditional coverage of the tools of the trade (botanic gardens, herbaria, libraries, nomenclature), which are often not covered in equivalent texts; and chapter 10, Taxonomy in the Service of Man (9 pages), is an attempt to explain the usefulness of taxonomy in the modern world, concluding with a plea for more monographic treatments rather than floras (including an outline of the plan that officially emerged as the Species Plantarum Project). The appendix is a very brief outline classification of the plant kingdom.
This is, ultimately, a pretty good attempt to provide a readable introduction to plant systematics, but its idiosyncrasies need to be taken into account when recommending the book to other readers. Firstly, there are definite biases in the coverage of the various topics. This is presumably a product of Stace's own interests, so that topics of personal interest, such as cytogenetics and chemotaxonomy, get a larger slice of the cake at the expense of more recent techniques. The discussions of recent developments read as though they are insertions into the second edition, rather than being integral parts of the original plan for the text. This unfortunate arrangement contradicts the stated aim of presenting taxonomy as a contemporary methodology.
Secondly, Stace has his own personal viewpoints, which necessarily colour the conclusions that he reaches. These viewpoints are fairly traditional, with modern methods often being viewed as interesting (although valuable) curiosities that are unlikely to replace the more traditional techniques. The fact that phenetics, cladistics and vicariance biogeography are all explicit attempts to move taxonomy into the modern world of scientific hypothesis-evaluation is not mentioned at all, and the usefulness of computers (both in analysis as well as in identification and databasing) is grossly under-estimated.
Thirdly, the more recent techniques of analysis (notably cladistics) are consistently mis-represented in the text. For example, cladistics is described as a monothetic rather than polythetic analysis (and is criticized as such), which is only true if there is but one synapomorphy per branch on the cladogram; vicariance biogeography and panbiogeography are treated as equivalent techniques of analysis (which would have made Leon Croizat's blood boil); and vicariance biogeography is presented as treating dispersal as unlikely (rather than as merely untestable).
Finally, while most terms are explained clearly when they are first used, there is a persistent use of unexplained terminology, which is very disconcerting. Stace also has a tendency to spend a large proportion of each page defining categories and terms, which can be somewhat overwhelming, and I do not always agree with his definitions and terminology.
So, in spite of the author's claims to the contrary, this book is not really concerned with taxonomy as a modern science, but is more a reflection of the author's own research interests. The aim of being an introduction to taxonomy as a part of contemporary science could be better achieved by reducing the amount of detail in chapters 5 & 6, and then using the space gained to present more balanced treatments of recent techniques such as DNA sequencing, cladistics, and vicariance biogeography. With only a relatively small amount of re-writing, these contemporary methods could easily be represented as explicit attempts by taxonomists to revolutionize their practices, and thus show the world that we are no longer just stamp-collectors.
Reviewer: David Morrison