Fresh approach to the study of fossil plants

The Evolution of Plantsby K.J. Willis and J.C. McElwain, Oxford University Press, 2002. $40.00/£22.95 pbk (x + 378 pages) ISBN 0 19 850065 3View Large Image | Download PowerPoint SlideThe focus of this interesting and readable new book in paleobotany is evolution. This focus upon evolution requires that a great deal of attention to be given to the ecology and functional morphology of plants through time. It is these aspects of The Evolution of Plants that make it so interesting and informative. The major themes presented in the book are how fossils are formed, early life, colonization of land, early trees, seed plant evolution, flowering plant origins, mass extinctions, ancient DNA, and evolution theory applied to the fossil plant record. This organization is logical and breaks away from the more common organization of paleobotany textbooks along phylogenetic lines. The increasing complexity of plant life through time tends to provide a sequence in this book that parallels the modern classification of plants. It includes many cladograms and charts showing the natural relationships of plants.The presentation of major trends in the evolution of plants carries the reader through time and increasing complexity of the structure, reproductive biology and the development of plant communities and plant–animal interactions. Attention is also given to CO2 fluctuations and major pulses in the abiotic world. Plant fossil records are mapped in relation to the CO2 estimates several times in an effort to demonstrate how the evolution of plant taxa relate to the CO2 environments in which they evolved. Paleovegetation world maps are frequently presented showing the distribution of various fossil assemblages at different ages in Earth's history from the early Devonian through the Miocene. The evolution of plants presented in graphic form in relation to their environment and their geography allows the reader to comprehend the whole of the Earth's vegetation as it changed through time. This concept is further emphasized by the repeated presentation of charts showing the species abundance of each major plant taxa through time. The book is well illustrated with figures, diagrams and reconstructions. Although many are redrawn from various textbooks and papers and vary in quality, they are all informative and add to the book's usefulness. However, changes in the proportions of some redrawn figures (such as Figure 6.3) alter the nature of the original reconstruction.As with any first edition of a new book, there is bound to be some omissions and minor copy mistakes (Proauaucaria should be Pararaucaria, Figure 1.4). A few of the omissions should be mentioned because they are important events in the evolution of plants. When discussing the evolution of heterospory it would be useful to mention the independent and parallel evolution of the megaspores and microspores found in the late Devonian aquatic heterosporous lycopods [1xThe functional biology of Devonian spores with bifurcate processes – a hypothesis (Essays in Evolutionary Plant Biology). Dilcher, D.L. et al. The Palaeobotanist. 1992; 41: 67–74See all References][1] and the Cretaceous aquatic heterosporous ferns. Important steps in the evolution of pollen are also omitted. It is significant that Gingko and the cycads still reproduce by ancient prepollen, dating from Permian times [2xZoidogamy in fossil gymnosperms: the centenary of a concept, with special references to prepollen of late Paleozoic conifers. Poort, R.J. et al. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 11713–11717Crossref | PubMed | Scopus (32)See all References][2]. In addition there is no clear focus upon the closed carpel as the important defining character of angiosperms. This key character was used to define Archaefrutus as one of the oldest known early angiosperms. However, no mention is made of Archaefrutus [3xIn search of the first flower: a Jurassic angiosperm, Archaefructus from N.E. China. Sun, G. et al. Science. 1998; 282: 1692–1695Crossref | PubMedSee all References][3] in the section ‘Evidence for the first Angiosperms’ or ‘Flower parts’ in Chapter 6. Instead, it is considered along with the problematic angiosperms Crinopolles and Furcula.Extreme care needs to be taken when drawing direct relationships from the fossil record to extant taxa at the generic level. There seems to be a tendency in this book to relate early fossil angiosperms to extant taxa and then assume that an extant family, the Platanaceae (Table 8.3), has been in existence for 120 million years. This practice is what led Ledyard Stebbins to ignore the fossil record when writing about angiosperm evolution [4xToward a new synthesis: major evolutionary trends in the angiosperm fossil record. Dilcher, D.L. : 255–270See all References][4].This book is a welcome addition to paleobotany. The chapter summaries and the glossary are useful parts of the book and make it attractive to students. It is a book that should be used in the classroom when teaching classes in plant evolution, paleobotany, phytogeography and plant morphology. It is useful as a general reference for plant evolution rather than a reference manual about the details of fossil plants that are cited frequently in the text.