Plant Systematics: A Phylogenetic Approach

Plant Systematics: A Phylogenetic Approach , 3rd edn . By Judd, W. S., Campbell, C. S., Kellogg, E. A., Stevens, P. F., Donoghue, M. J. , Sinauer Associates Inc. , Sunderland, MA . Hardback, ISSN 978-0-87893-407-2 , 2007 , $94.59 , 611 pp . In August of 2007 Sinauer Associates released the third edition of Plant Systematics: A Phylogenetic Approach by Judd et al. Compiled by five authors, each an expert in complementary aspects of plant systematics, the book builds from the 1999 Engler Award-winning first edition and continues to target undergraduates in plant systematic biology courses. In many areas the text and examples go beyond the coverage likely to be incorporated in the average undergraduate class and ultimately this represents a valuable resource for the graduate student and practising plant systematist. This review will provide a basic outline of the topics covered in the book, updates relative to the second edition, my perception of its strengths and weaknesses, and a discussion of how the text compares with the currently available competition in the undergraduate plant systematics textbook market. The book’s nine chapters and two appendices lead the reader from the fundamentals of systematic biology through an in-depth treatment of the angiosperm branch of the Tracheophyta. The overview of the basic concepts and importance of plant systematic biology in Chapter 1 establishes the fundamental role of modern phylogenetics in classification, nomenclature, biogeography, evolutionary biology, ecological diversification, and ethnobotany. In the last section of the chapter the authors also provide a useful overview of the book’s organization to help the reader. Chapter 2 delves deeper into the principles and methods of modern systematic biology. This begins with coverage of heritable character data, moves on to the inference of trees, and continues with a discussion of outgroups, tree selection, homoplasy, and basic metrics by which trees are compared and clade support assessed. The chapter ends with the connection between phylogeny and classification. Although readers of Cladistics may not find the chapter sufficient, the authors have succeeded in presenting most of the basic material at the undergraduate level. In addition, ample literature citations direct the interested student to further reading. The discussion of the history of plant systematics and systematic biology in Chapter 3 is a pleasure to read and ultimately covers the people and developments in a useful and interesting manner. Coverage includes an historical consideration of classification, stability, the development of phylogenetic inference, and alternative classifications through time. Chapters 4 and 5 provide a discussion of alternative classes of character data. The former begins with an extremely useful illustrated glossary of plant morphology followed by discussion of pollination syndromes. A series of short sections focused on inflorescence structure, fruit types, anatomy, cytology, embryology, palynology, and secondary metabolites follows. Although some coverage of the latter topics is brief, the literature cited provides additional direction for further reading. Overall, the illustrations, text boxes, and descriptions in Chapter 4 represent a tremendously useful resource for the student of plant systematics. Issues relating to molecular character data are reserved for Chapter 5. This discussion provides a strong introduction to DNA sequence data, specific issues relating to the three plant genomes, and commonly applied loci in plant systematics. Coverage of phylogenetic analysis of molecular data (e.g. alignment, models, gene-trees/species-trees) is mostly sufficient for the undergraduate introduction, but they are inadequate as a useful long-term reference for the owner. In my view, the unique strengths of the book begin to reveal themselves with Chapter 6, “The Evolution of Plant Diversity”. This segment provides an excellent “short course” on the mechanisms and driving forces commonly discussed in plant evolutionary biology. Relevant coverage of the importance of hybridization, introgression, and polyploidization are well supported with interesting examples and carefully conceived figures. The bulk of what follows, nearly 400 pages in Chapters 7–9, includes coverage of Tracheophyta phylogenetics and characteristics of major groups down to the level of family. This component includes keys, explicit reference to over 170 families (c. 30 non-angiosperm and 140 angiosperm), and discussion of the number of genera/species, critical morphology, economically important members, relevant literature, and the relative support for inferred relationships. Representing a monumental synthesis of information, these chapters are the heart of the book. They not only impart critical information but illustrate the application and practice of modern systematic biology through the discussion of phylogenetic studies and inferred evolutionary patterns. Those familiar with the previous editions of Plant Systematics: A Phylogenetic Approach will immediately notice the addition of colour throughout. By increasing the number of colour figures and photographic plates the authors and publisher have enhanced their ability to convey information and the general aesthetic of the book for a nominal increase in price. Numerous changes and additions keep the reader abreast of developments in our understanding of relationships (largely incorporated in Chapters 8 and 9) and, for example, the availability of large numbers of complete plant genomes for phylogenetic studies (Chapter 5). From the instructors point of view, the development of the “Instructor’s Resources Library” CD (PowerPoint and JPG files for all line art, photographic plates, and tables––available to instructors on request) is extremely valuable. Furthermore, the “Photo Gallery” CD, introduced in the second edition, has continued to grow (3100 images, 1900 spp., and 185 families) and represents an easy-to-use resource for instructors and students augmenting photo collections and study tools from those available online (e.g. http://www.plantsystematics.org). When considering the authors’ stated objectives, I was hard-pressed to identify many significant problems or disappointments. Of those, one specifically relating to the interests of the readers of Cladistics is the coverage of Hennig’s contributions to systematic biology. Attention to the issue of special similarity and its importance to the development of phylogenetic theory are provided in parts of the first three chapters, with the primary focus on “Hennigian Argumentation” in Box 2A. Unfortunately, this treatment is not as clear as it might be. The pertinent topics and debates are introduced; however, the uninitiated may overlook the essential distinction in grouping information provided by special similarity when compared with overall similarity. This is particularly true in Box 2A, which discusses Hennig’s development of the concept of synapomorphy, but the topic is obscured by an initial focus on aspects of rooting and polarity that Hennig addressed, but that are unnecessary when attempting to illustrate Hennig’s fundamental contributions that endure in modern practice. A second concern was with the brief and partial description of gene-trees and species-trees in Chapter 5. The combination of incomplete coverage (e.g. no discussion of orthology and paralogy) and the use of a complicated example may lead to confusion among students. In my view, these topics are sufficiently fundamental in modern systematic biology to warrant further clear discussion. Lastly, being written by a group of experts comes with obvious benefits (see above) and a few potential drawbacks. The only items worth noting in this context are the presence of some minor inaccuracies that are probably the result of individual authors focusing on their own chapters and a bit less on integration and consistency among chapters. An example presents itself when comparing fig. 1.1 and various figures and discussion in Chapter 7. The evolution of xylem and phloem is noted to have occurred within the “bryophytes” in fig. 1.1. However, the figures and discussion in Chapter 7 clearly describe that “bryophytes” are not considered to have homologous vasculature to members of Tracheophyta. A few other editorial issues have slipped through; those of us using the text may wish to point out problems with fig. 2.7 (autapomorphy inadvertently equated with synapomorphy), fig. 2.21 (two different representations of the same phenetic distances that are not equivalent), and an inaccurate verbal definition of the retention index (p. 23). These are nitpicky details in an excellent text. As part of this review it seemed useful to consider how the third edition of this text measures up against the available competition. To the best of my knowledge, there are two primary competitors in the undergraduate plant systematics textbook market––Walters, Keil, and Murrell’s Vascular Plant Taxonomy and Michael Simpson’s Plant Systematics. When considering the topics covered and relative clarity of each, I concluded that all three are worth serious consideration. With regard to the fundamental topics incorporated, each serves the student and instructor well. Some discussion of each book’s relative merits may help those seeking a new text narrow in on the most appropriate option. Having not previously examined Michael Simpson’s Plant Systematics (Elsevier, 2006, MSRP $72.95 but available online for about $60), I was extremely impressed by the breadth of coverage, utility of figures, general readability of the text, and reasonable price. The coverage includes thorough introductory chapters on plant systematics and systematic biology. These sections are followed by a series of chapters encompassing plant evolution. Here the treatment is especially detailed, including aspects of life cycle and specifics of morphology that few instructors would be likely to cover in a single course focused on plant systematics. The treatment of c. 120 families follows the classification of the Angiosperm Phylogeny Group and is akin to the treatment in Judd et al. in clearly illustrating the practice of modern systematic biology. Simpson’s discussion and incorporation of literature cited associated with each family are excellent, but not as in-depth as the average treatment by Judd et al. Following the discussion of families, the author continues with several hundred pages associated with morphology, anatomy, physiology, embryology, palynology, reproductive biology, molecular systematics, nomenclature, collecting, herbaria, etc. The incorporated scope and detail make it a particularly apt choice for faculty seeking to use plant systematics as the focal point for a series of related botany courses. The text could function as the primary reading for many components of a traditional introductory botany course, most topics covered in a plant systematics course, and many components covered in a plant morphology and anatomy course. For 33 years Walters, Keil, and Murrell’s Vascular Plant Taxonomy (Kendall/Hunt Publishing, 2006, MSRP $80.95 in soft cover) has been a staple in many plant systematics courses. Now in its fifth edition, the coverage of c. 75 families includes more general description and discussion of fewer plant families than the other two books. This treatment is an explicit part of the authors goal “to prepare a text that can serve as an introduction to taxonomy and that is thorough enough to provide a solid background for students, but not so detailed that students feel overwhelmed…” They have truly excelled in their stated objective. This is an excellent book focusing less on phylogenetic systematics of angiosperms (i.e. limited specific discussion of current phylogenies and tested characters) as a topic and more on directed student learning of general systematic biology as well as plant families and associated identifying characteristics. Members of the Hennig Society will especially appreciate the opening line of the chapter entitled “Phylogenetic Classification”, in which the authors begin “In 1950 a German entomologist, Willi Hennig, proposed a new method of phylogenetic classification”. If the coverage matches your course goals, the newest edition of the book remains an outstanding option. In my view the relative strength of Plant Systematics by Judd et al. can be found in the 400 plus pages of synthesis on modern vascular plant classification and phylogenetics in addition to the clear discussion of identifying features for families, the instructors CD, and the photographic CD. The detail incorporated into the coverage of specific groups is considerably above what is likely to be offered in the average undergraduate course, but these added components are far from distracting. It is these sections, along with much of the introductory material, that will convince students to keep the text as a reference for the future and why many graduate students and faculty will purchase the book outside the context of an undergraduate course.