Book Reviews: Ecology, continued

Population Biology of Grasses Cheplick, G. P., ed., 1998. ISBN 0-521-57205-3 (cloth US$85.00) 399 pp. Cambridge University Press, 40 West 20th Street, New York, NY 10011-4211. - Field biologists often seem to regard grasses as something to be avoided or ignored, perhaps because of the perceived difficulty of identifying them. Perhaps this book will provide the extra motivation needed to overcome this aversion, because it provides readers with many fine examples of grasses as excellent 'model' organisms for studying ecological and evolutionary problems and as fascinating organisms in their own right. (And identifying grasses isn't that difficult - really!) Perhaps some readers may even be motivated to consider using a grass as a study organism. If so, they will discover what this volume demonstrates: that the Poaceae can provide the researcher with species that span a very wide range of life histories, breeding systems, and ecological roles an excellent family to go to if one has a 'shopping list' of criteria to meet in the choice of a study organism.

This breadth of life histories, breeding systems, and ecological roles is apparent in the chapters of this multiauthored volume. Because of this breadth, some of the chapters could even serve as good general introductions to their respective topics. Keeler's review of polyploidy in grasses is such a chapter, as are Godt and Hamrick's review of allozyme diversity in grasses and Baskin and Baskin's review of seed dormancy.

There are also chapters dealing with topics unique to grasses. Makita discusses the long-lived monocarpic bamboos of the genus Sasa, which may be unfamiliar to many western readers. Briske and Demer describe the relationship between ramets (individual stems), connected clusters of ramets, and genetic individuals - a topic that, while not unique to grasses, has been most studied in them. Clay reviews the relationships between grasses and the endophytic and epiphytic fungi that form symbiotic relationships with them, relationships that can vary from mutualistic to parasitic, sometimes in the same species.

Despite the book's title, it contains relatively little population ecology sensu stricto. Only the chapter by Orr has a substantial demography content. This excellent chapter, however, gives the reader a very interesting comparison between a short-lived species with frequent recruitment (Heteropogon contortus) and long-lived species within frequent recruitment (Astrebla spp.), all of these species being highly affected by grazing and by year-to-year variations in precipitation in tropical Australia. There is also little population genetics sensu stricto in this book, other than Godt and Hamrick's review of allozyme diversity.

With that caveat, there is quite a lot of very interesting and useful information in this book. In addition to the chapters already mentioned, there is a review of sex expression in grasses by Quinn that provides a particularly good synthesis of his extensive work with Buchloe dactyloides. Cheplick reviews seed dispersal and establishment of grasses. Newsham and Watkinson review the mycorrhizae associated with grasses, especially their direct and indirect effects on their hosts, with particular attention to the circumstances under which the association is or is not mutually beneficial. Gamier discusses nitrogen use. Lauenroth and Aguilera discuss inter- and intra-specific interactions, mostly competitive, between grasses and other vascular plants. Finally, there are two chapters that are best classified as community ecology, Wilson on competition between grasses and woody plants, and O'Connor and Everson on African grasses and grasslands; the latter chapter also includes some demographic material.

This book is obviously unified by the focus of all the authors on grass species. Other than that, however, there is little unity, despite a graceful introductory chapter by Bradshaw. The best argument for a book devoted to studies of a single plant family is provided by Godt and Hamrick, who point out that surveying a single family partially controls the potentially confounding effects of phylogeny.

In general the quality of the individual chapters is commendable, and the coverage of many is exceptional. However Cheplick's promise in the Preface to "bring together ideas from ... both basic and applied perspectives" is not kept: very few of the authors cited studies from the range science literature or other applied sources. (Orr, and O'Connor and Everson, are the exceptions; does this sav something about American setentists?)

The volume is in general well-edited, although I did find a few lapses. In particular, readers will find it helpful to know that Schizachyrium scoparium and Andropogon scoparius are the same species, as are Agropyron spicatum and Pseudoroegneria spicata; there may be other synonymies that I did not catch.

In conclusion, this book will be a valuable addition to my shelf as a ready source of literature reviews; I will also recommend it as a source of useful readings for graduate students. Most plant population and community ecologists and evolutionary biologists will find chapters that are of considerable interest to them, whether or not they have any interest in grasses per se. I would also like to recommend this book to anyone who has held back from studying grasses but may be convinced by this volume of their potential as research organisms. - Norma Fowler, The University of Texas, Austin

Neotyphodium/Grass Interactions Bacon, Charles W. and Nicholas H. Hill, eds. 1997. ISBN 0306-45688-5 (cloth US$129.50) 452 pp. Plenum Press, 233 Spring Street, New York, New York 10013-1578. -The systemic endophytic fungi that are currently known to inhabit the leaves of hundreds of grass species had been described as a group some time ago, but only in the last 20 years has interest in this symbiosis resulted in intensive investigation by botanists, mycologists, and agricultural scientists. This is partly because fungal endophytes affect not only the biochemistry, physiology, and growth of their hosts, but they also impact many herbivores from insects to mammals that feed on grasses. The "virtual explosion of research literature" (to quote from the editor's Preface) on the nature of the endophyte/grass interaction and its agricultural and ecological implications has resulted in a vast and diverse body of technical papers distributed across a wide spectrum of journals devoted to both basic and applied research. Much of this modern effort has been devoted to endophytic fungi in the newly-erected genus Neolyphodium (formerly Acremonium) in the family Clavicipitaceae, because these endophytes are symbiotic with economically important forage and turf grasses, especially tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne).

This massive volume contains 73 contributions that represent the "Proceedings of the Third International Symposium on Acremonium/Grass Interactions" held 28-31 May, 1997 in Athens, Georgia. The chapters range enormously in length from 1 page (!) to 36 pages, but many are 2-3 pages long. The chapters are not organized by content and there is only a brief, 2-page index. Both of these factors are likely to make it difficult for a reader to quickly locate specific information on a selected topic. There are many specific, short research reports and a few reviews (egs. G.C.M. Latch provides an "overview of Neolyphodium-grass interactions"; H.H. Wilkinson and C.L. Schardl explore the "evolution of mutualism in grass-endophyte associations"; D.L. Cross reviews "fescue toxicosis in horses"). A fair number of the short reports adhere to a research paper format (Introduction, Methods, etc), but because of their brevity, many papers lack methodological detail and/or a discussion section. The literature cited sections are generally very brief (3-10 citations) or absent altogether.

The authors use a diversity of approaches, including molecular, systematic, physiological, and ecological investigations. Topics covered include (1) endophyte effects on grass-feeding herbivores (Eerens et al. on sheep plus 20 other chapters), (2) the distribution and biochemistry of the herbivore-deteffent alkaloids produced by endophytes (A.E. Glenn and C.W. Bacon on alkaloid distribution plus 9 other chapters), (3) endophyte distribution and the ecological implications of endophyte-grass interactions (K. Clay on biodiversity plus 8 other chapters), (4) endophyte effects on host physiology (G.W. Buck, C.P. West, and H.W. Elbersen on drought tolerance plus 7 other chapters), and (5) endophyte systematics (J.F. White, Jr). Other areas covered are new techniques for detecting and quantifying Neotyphodium (including an intriguing chapter by S. Logendra and M.D. Richardson on the possible use Of ergosterol as an indicator of endophyte biomass), the significance of "endophyte toxicosis" (i.e. the detrimental effects on mammalian herbivores) in different parts of the world (4 chapters), and the use of endophytes for pasture (L.R. Fletcher and H.S. Sydney) and turf improvement (C.R. Funk and J.F. White, Jr).

Although it is likely that no student of endophytes would find every chapter useful or informative for a particular research project, the editors have succeeded in bringing together a tremendous amount of information on the latest research in this area from a geographically diverse group of scientists. As the editors point out in the Preface, initial research efforts on endophyte-grass relations were mostly conducted in the United States and New Zealand because of the economic importance of endophytes to the livestock industries. However, endophytes are now being investigated on all "six of the habitable continents". Thus, although the present volume has the usual U.S. and New Zealand emphasis, there are also contributions from investigators in China, India, Morocco, Spain, and South America.

The editors should be commended for the timely manner in which this volume was produced, less than a year after the symposium on which it was based. Perhaps because of its rapid publication, there are a fair number of typographical errors, but most of these are relatively minor and do not detract from the generally excellent presentation and clear graphics. The most major misprint involves one paper (E.E. Hiatt III and N.S. Hill on mycelial protein and plant mass effects on alkaloid concentration) that is repeated, comprising Chapters 28 and 46!

Any graduate student who is considering (or performing) a project that involves endophytic fungi can turn to this book for an overview of the state-of-the-art in selected areas of modem endophyte research. However, it should be noted that the focus is on Neotyphodium and its primary hosts (fescues and ryegrasses) and does not provide a synthesis with respect to the ecology and evolution of the many endophyte/grass interactions that have been described to date. This may, in part, reflect our general ignorance of the significance of endophyte infected grasses to ecological and evolutionary processes in grass-dominated ecosystems. As can be seen in this book, we also lack an understanding of the mechanisms of endophyte-mediated effects on host grasses; to paraphrase what one endophyte researcher recently told me "The easy, descriptive work on endophyte effects has been done; now comes the hard part of determining how endophytes do what they do!" Because of the focus on Neotyphodium/grass interactions, most contributions necessarily have an agricultural orientation. Of course, another consideration in deciding whether or not to purchase this volume is the hefty price tag. Despite these limitations, this book should provide much of interest to any investigator examining multitrophic interactions, especially those involving animals, plants, and fungi. - Gregory P. Cheplick, Department of Biology, College of Staten Island, City University of New York, Staten Island, NY

Plant Life Histories: Ecology, Phylogeny and Evolution Silvertown, J., M. Franco and J. L. Harper, eds., 1997. ISBN 0-521-57495-1 (Paper US$29.95) 313 pp. Cambridge University Press, 40 West 20th Street, New York NY 10011. - This book represents a moderately successful attempt at integrating some of the latest research in plant evolution, ecology and systematics as it relates to life history traits. Although not a collection of papers presented at a symposium, it has much of the same flavor as that kind of publication. With fifteen chapters, each written by different authors (many of them leaders in their specialties), divided into five sections, it suffers from some of the weaknesses of many other multi-authored books. Some of the chapters are readable by anyone with a reasonably good background in botany and ecology, whereas other chapters will be nearly unreadable by all but those knowledgeable in the particular subspecialty being covered. A prime example of one of the more readable chapters is chapter 14, "Evolutionary trends is root-microbe symbioses" by Fitter and Moyersoen. I only know the basics of mycorrhizal symbiosis and I found that this chapter easily drew me into the subject. Examples of the less readable chapters include a few that are presentations of mathematical models for the evolution of various life history traits. These chapters require an extensive background in mathematics and population genetics to be understood.

Most of the chapters dealt with one or more aspects of plant life history traits such as longevity, fecundity, seed size and mass, and seed dormancy. A common thread that seems to weave its way through many of the chapters was incorporation of the latest phylogenetic information available into their hypotheses concerning evolution of life history traits. Many authors used the seed plant phylogeny of Chase et al. (1993), which was based on rbcl gene sequences for 499 taxa, as their estimate of plant phylogenetic relationships. Although Chase et al. (1993) carefully point out the weaknesses of their analysis, it was still the best "deep" phylogeny available and likely represents a reasonable phylogeny for the seed plants.

The importance of using reliable phylogenetic information in studies of character evolution is best presented by Silvertown and Dodd in chapter 1. They point out that because common descent confounds the analysis of character evolution, phylogenetic relationships must be taken into account when proposing any hypotheses of how characters have evolved. Their innovative approach to this problem is to test for correlation or association between "trait contrasts" instead of simply between trait values. In brief, trait contrasts are determined by comparing trait values between sister taxa at all levels within a phylogeny. In other words, taxa are not treated as single, independent data points, but must be interpreted in a phylogenetic context. Many of the other authors in the book use this kind of approach in their correlations. Westoby, Leishman and Lord (chapter 8), although not completely discounting the trait contrast approach, suggest that it gives results that are too conservative for many kinds 6f trait analysis. They even go a step farther and suggest that correlation analyses of "natural" data, in general, are insufficient to make solid hypotheses of causation and must be supplemented with controlled experiments. It is refreshing to see such a broad range of opinions being expressed.

The overall tone of most of the authors is that botanists are making progress in the study of the evolution of life history traits in plants, but that we have a long way to go. More specifically, the results of many of the correlation studies are ambiguous and even contradictory at times; the enormous problems involved in designing controlled experiments that incorporate enough experimental treatments to be significant have yet to be solved; and the mathematical models, although excruciatingly complex in appearance are, in many ways, gross simplifications of genetically and ecologically complex systems. This book seems to portray an accurate picture of the current state of evolutionary life history studies in plants.

There is also a certain sense in which this book was an attempt to reach as broad an audience as possible. Inclusion of chapters dealing with insect-plant interactions and root-microbe symbioses seem to reflect this. I found both chapters interesting and informative, but they seemed somewhat oblique to the major emphasis of the rest of the book. There is also a bias that is not evident from the title. Essentially every chapter deals with life history of seed plants. Pteridophytes and non-vascular plants are never mentioned. Maybe the title should have been "Seed Plant Life History Traits."

In spite of the uneven content from chapter to chapter, this book still represents a good overview of current research on plant life history traits and will be appreciated by plant ecologists. Botanists from other subdisciplines will find at least some of the chapters of interest as well. Undergraduate, and beginning graduate students, will probably find much of the book challenging reading. - Bryan Ness, Department of Biology, Pacific Union College, Angwin, CA

Literature Cited

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