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ASBS Newsletter – Book Review

Biological Systematics. The State of the Art

written by Alessandro Minelli

(From ASBS Newsletter Number 95, June 1998)

Publisher: Chapman & Hall, London. 1993. xvi+387 pp. ISBN 0-412-62620-9.

This is the second book on biological systematics, as opposed to botanical systematics, in this renewed series of reviews. The previous review (ASBS Newsletter 93: 53-57) considered one of the better-known books (by Donald Quicke), often recommended as a textbook. I concluded that this book was probably quite acceptable as an introductory textbook, but that it has certain obvious biases (e.g. entomology, parsimony cladistics) as well as weaknesses (e.g. typographical errors, poor coverage of some important topics). It was thus, in many ways, a compromise between several competing influences (e.g. botany versus zoology, detailed versus broad coverage); but that seems to be the inevitable fate of undergraduate textbooks.

The book by Alessandro Minelli is a very different kettle of fish. He doesn't even attempt to present an introduction to everything, reasoning that to do so would produce a superficial treatment. Instead, Minelli's avowed aim is to present all of the "main facets of biological systematics" as an essay for reading (and discussing) rather than for use as a reference book. He claims to have "sacrificed depth of treatment to the advantage of broadness of coverage", but you will find that this is often a very modest appraisal of his work.

So, the book is neither a real textbook for an undergraduate biology course nor a real reference book. Instead, it is aimed at "fellow systematists, [and] other people in the field of evolutionary biology or in biology at large, who are interested in getting a comprehensive idea of what is occurring today within the broad field of systematic biology". The subtitle of the book is therefore something of a pun - the author's emphasis is that, as a result of "tremendous developments, not just since Aristotle or Linnaeus, but particularly in the last two or three decades", systematics is no longer an art (as opposed to a science) but that it is now up-to-date and uses state-of-the art equipment and techniques. Minelli certainly is at pains to emphasize and re-emphasize that systematics is a scientific pursuit, or at least that it should be.

I should therefore start by saying that I like this book very much. In particular, the author has achieved what he set out to do - to write an essay (or set of essays) that could serve as a focal point for discussions of the various topics of current interest in systematics. He has clearly steeped himself in the literature, with particular attention to rarely-quoted non-English sources (some of which are provided with new translations for their quotations in this book), and the references cited make his discussions excellent introductions to the topics that he covers. The topics include all of those that should be included in a broad concept of what constitutes systematics, although everyone will find some of their own pet issues ignored. The author holds very firm views on each of the topics, and never fails to let you know where he stands. However, there are no obvious taxonomic biases, and the examples are drawn with equal facility from micro-organisms, invertebrates, insects (the author's own area of expertise), vertebrates, fungi, and plants - Minelli even recognizes when botanists and zoologists do things differently as a result of the nature of the organisms they are dealing with. There is, though, a very strong evolutionary bias - cladistics is taken as a self-evident part of systematic work, as "systematics (according to its very name) should proceed with building up a phylogenetic system of monophyla".

The problem with the book, if one is to be identified, is that it is sometimes difficult to find a thread uniting all of the different topics covered. Any single chapter can be read on its own, and can be very interesting as such; but it is often problematic to work out why those topics are gathered together in the same chapter, and why that chapter was included at that place in the book as a whole. Neither the introductory nor the postscript material really addresses this issue, nor does the division of the book into three Parts (Problems and Methods; The State of the Art; Epilogue). If a book is to be taken seriously as a coherent whole, then a structure needs to be clear; and the lack of structure here definitely makes the book look more like an aggregation than an entity.

Another quibble would be the essay or review-like nature of the book. This format means that there are almost no illustrations to break up the text, although there are plenty of tables (some of them covering several pages, and which are only referred to almost as an aside!). There are also many lengthy quotations, something that readers of the journal "Systematic Biology" have come to expect but not necessarily book readers. Nevertheless, the publication quality of the book is good, with relatively few typographical errors. The three indices (author, subject, taxonomic) are effective; but the inclusion of a glossary would have been very helpful, as many technical terms are introduced without explanation. Also, the reference list is very erratically alphabeticized, with, for example, De Pamphilis and De Pinna under "d" and De Queiroz under "q".

The book starts with a consideration and comparison of Systems and Classifications (12 pages). Classifications, the arrangement of taxa into a hierarchical set of classes, is usually seen as the obvious outcome of systematic work, but this is not the only (nor necessarily the best) way to represent the results of systematic analyses. In particular, the representation of the structure of the living world as being the result of natural processes, such as inter-breeding and common descent, is not easy when the output is constrained by the Linnean concept of classes. It then becomes an important point whether scientific systematics, which is involved with the production of systems representing evolutionary history (currently using trees as the representation), should be divorced from the production of commonly-used classifications. In this chapter, the discussion of the problems of systems versus classifications is facilitated by a broad overview of the development of consequential concepts (such as keys versus hierarchies), along with a debate concerning the practical uses to which systematics is put. As far as classifications are concerned, Minelli suggests that "consensus is dangerous in science, but can sometimes be useful in practice. Accordingly, consensus approaches cannot shape systematics, but they can help to obtain a classification for applied purposes. Both aims (science and applied use of scientific knowledge) are worthy of effort, provided that their non-equivalence is always borne in mind."

Chapter 2, Some Steps in Comparative Biology (29 pages), considers the data and analyses used in systematics, including the concepts of characters, monophyly, polarity, and cladistics. Each of these topics has a good introduction, but rarely is the topic covered completely. For example, an informational concept of homology is preferred to an historical one, and therefore primary versus secondary homology is not touched. Furthermore, the inclusion of topics sometimes seems to be rather arbitrary; and some of the topics are not as contemporary as might be liked, either. For instance, much is made of pattern cladistics, and yet this has become somewhat irrelevant with the development of explicit models for molecular data (nowhere is this change more obvious than in the update of the chapter on phylogenetic analysis between the first and second editions of the "Molecular Systematics" book).

As usual with introductory books, the discussion of cladistics is the most deficient part of this chapter. For example, distance methods are treated as being phenetic because they "do not acknowledge character polarity", whereas polarity actually comes from the choice of outgroup not from the method of tree construction. Furthermore, distance methods are claimed to be popular for the analysis of molecular data because some molecular data come only as distances, whereas it is popular because the use of explicit models of evolution allow problems of inconsistency to be overcome. As well, the production of multiple equally-optimal trees is discussed as though it is a problem peculiar to parsimony methods, as is the problem of inconsistency resulting from unequal evolutionary rates along branches, both of which in reality affect several tree-building methods. The lack of understanding of the problems of consistency re-appears later in the book, for example in the discussion of the molecular data favouring birds+mammals as a monophyletic group, which has now been shown to be based on the similar GC-content of homeotherms affecting the cladistic analysis.

The chapter on Biochemical and Molecular Systematics (18 pages) is possibly the weakest one in the book, because its coverage is now rather out-of-date. The discussion itself is very balanced and fair, but the topics covered and the references cited often do not deal with true contemporary issues. Along with this, the discussion often reads like a summary of the results of selected papers rather than a synthesis of ideas - however, this might just reflect the volatile nature of the topic rather than an inherent inadequacy in the book.

Minelli gets back into stride with the chapter on The Species (25 pages), but even here there is no real context for the chapter, with no real explanation for why this group of topics was included together. The reader will, nevertheless, learn a lot about species concepts, intra-specific diversity, hybrids, and speciation. The only obvious weakness is that the non-hierarchical nature of much of intra-specific variation is treated as an aside, whereas it deserves detailed consideration.

Resources and Media (17 pages) covers people, institutions, literature, and nomenclature, with most of the pages devoted to the latter topic. Much is made of organisms with both botanical and zoological names, but nowhere is it mentioned that protistologists (for example) tend to ignore the rules of nomenclature completely. The consideration of a consensus system of biological nomenclature is timely, but nothing is said about non-binomial names. Minelli also has to be forgiven for using the word "museum" to refer collectively to museums, herbaria and culture collections.

The Inventory of Natural Diversity (23 pages) is a good coverage of just where systematics fits into the biodiversity debate, with yet another quantitative answer to the question: "How many species do we know?"

In many ways, Towards the System (38 pages) is the heart of this book, although it is the least essay-like part of it. It provides an interesting historical summary of the classification of each major group of organisms, along with an extremely useful introduction to the most recent literature. Furthermore, there are some example classifications in the Appendices (55 pages), although these are not intended to serve as a new classification scheme. If you need a guide to a group of organisms with which you are not familiar, then this is as good a place to start as any. There is even a consideration of the practical problems, such as that of blue-green algae (which have to be typified with a living culture if they are treated as bacteria but with a herbarium specimen if they are treated as algae). In this chapter, Minelli needs to be forgiven for the comment that "many of these problems [with angiosperm classification] are simply the result of an unwillingness to reclassify angiosperms using phylogenetic systematics. Things are changing, however." Indeed!

The next three chapters are the most eclectic in the book. It is unclear why they are here, although each on their own is quite interesting. The first, Interviews on the Daily Work of Systematists: Problems and Trends (17 pages), considers practical aspects of being a systematist, and whether different taxonomic groups are treated in different ways by the people working on them. The Unequal Distribution of Taxonomic Diversity (13 pages) continues the same theme, by comparing large versus small genera and families. Finally, Domesticated Animals and Cultivated Plants (8 pages) covers the practical problems associated with the nomenclature of these organisms.

The book ends with Some Dangerous Trends and a Hope for the Future (6 pages). The trends turn out to be the fact that systematists are often less-than-critical about what they do, and that there is often a big gap between theory and practice, and between practice in one group of organisms compared to another, while the "hope" consists of only one sentence (that things are getting better). The dangerous trends are quite real - systematists have a less-than-worthy reputation as being natural historians rather than scientists, and a critical self-appraisal with respect to methodology and data would therefore not go astray. The hope is to be sincerely wished for, but only time will tell whether it becomes a reality.

So, in the final analysis, this is a very interesting book, which all practising systematists and research students would find of value. Any systematist who is at all interested in the theoretical and practical development of their science will find a wealth of thought-provoking ideas within the covers. Therefore, it would also serve as a good focus for a postgraduate course in systematics (although such a thing does not appear to exist in Australia). Much of the value of the book would probably be wasted on undergraduate students, as the topics are not introduced in the fashion expected from textbooks; however, the undergraduates would certainly learn a lot if they took the time to understand the author's approach.

Reviewer: David Morrison
Department of Environmental Sciences
University of Technology, Sydney