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Hybrid Zones and the Evolutionary Processs by R. G. Harrison Review by: Jitka Štěpánková Folia Geobotanica & Phytotaxonomica, Vol. 31, No. 1, Adaptation Strategies in Wetland Plants: Links between Ecology and Physiology. Proceedings of a Workshop (1996), pp. 166-167 Published by: Springer Stable URL: http://www.jstor.org/stable/4181432 . Accessed: 14/06/2014 18:18 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. . Springer is collaborating with JSTOR to digitize, preserve and extend access to Folia Geobotanica &Phytotaxonomica. http://www.jstor.org This content downloaded from 62.122.78.91 on Sat, 14 Jun 2014 18:18:00 PM All use subject to JSTOR Terms and Conditions

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Hybrid Zones and the Evolutionary Processs by R. G. HarrisonReview by: Jitka ŠtěpánkováFolia Geobotanica & Phytotaxonomica, Vol. 31, No. 1, Adaptation Strategies in Wetland Plants:Links between Ecology and Physiology. Proceedings of a Workshop (1996), pp. 166-167Published by: SpringerStable URL: http://www.jstor.org/stable/4181432 .

Accessed: 14/06/2014 18:18

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

.

Springer is collaborating with JSTOR to digitize, preserve and extend access to Folia Geobotanica&Phytotaxonomica.

http://www.jstor.org

This content downloaded from 62.122.78.91 on Sat, 14 Jun 2014 18:18:00 PMAll use subject to JSTOR Terms and Conditions

166 Bookreviews

based on phylogenetic trend (K. Periasamy), Section IV. Phylogenetic development: 16. Reconstruction of the phylogeny of seed plants (A.D.J. Meeuse).

Not only does the book endeavour to include scientists from different fields to ensure an interdisciplinary approach but the selection of authors covering almost all continents creates a world-wide international interdisciplinary forum. Such an approach has become essential in recent decades yielding new concepts and furthering on understanding of processes. The book is a valuable reference giving a review of a wide-range of aspects of growth processes. It is also very valuable for emphasizing the necessity of incorporating the structural background into the interpretation of physiological and biochemical results in experimental botany. In conclusion the book shows that results of work describing functions are incomplete if structural analysis is ignored.

Jana Albrechtova

R.G. Harrison [ed.]: HYBRID ZONES AND THE EVOLUTIONARY PROCESSS; Oxford University Press, New York, Oxford, 1993, 364 pp. Price GBP 45.-, ISBN 0-19-506917-X

Hybridization is the theme of this book, which resulted from a symposium entitled "Hybrid Zones and the Evolutionary Process" at the Fourth International Congress of Systematic and Evolutionary Biology (ICSEB) in College Park, Maryland, held in July 1990. It consists of 12 contributions and includes both botanical and zoological studies.

The book is divided into two major parts. Part I "Hybrid zone Pattern and Process", which comprises four articles, concerns general problems and the evolutionary significance of hybridization. Part II "Case studies of hybrid zones" gives a survey of different approaches to the study of various aspect of hybridization using examples of particular groups of both plants and animals.

Part I starts with the article "Hybrids and hybrid zones" by R.G. Harrison. Great attention is paid to a description of the fundamental terms, such as hybrid and hybrid zone, and the major issues in hybrid zone research are also discussed. While Chapter 1 considers the wider questions of hybridization, Chapter 2 "Genetic analysis of hybrid zones" by Barton and Gale focusses on the practical issues involved in genetic analysis of hybrid zones. Using various methods to describe the frequency of genotypes in hybrid zones, the authors illustrate how the research of hybridization between pairs of populations can contribute to our knowledge about the processes that keep them distinct and that presumably form the basis for separating full species. Howard in his article "Reinforcement: origin, dynamics, and fate of an evolutionary hypothesis" summarizes and analyses existing knowledge about the process of reinforcement - the evolution of prezygotic barriers to gene exchange in response to selection against hybrids.

Chapter 4 focusses especially on the problems of hybridization and introgression in plants. Rieseberg and Wendel in their article outline the historical development of ideas regarding introgression in plants, examine the evidence for its extent and discuss its potential consequences for plant diversification and speciation. Special attention is paid to the use of new methods of molecular techniques, such as chloroplast and nuclear DNA restriction fragment length polymorphism (RFLP), and random amplified polymorphic DNA (RAPD), in hybridization research. This article is completed by 308 references.

The most useful part of this book is the series of eight case studies devoted to particular questions of hybrid zone research. Despite the fact that hybridization is a widespread phenomenon in plants, the only paper dealing with issues of natural hybridization in plant populations occurs involved in this section: the genetic interaction between species of Louisiana Iris is used as a classic example of plant hybridization and introgression in the paper by Arnold and Bennett. Based on the genetic and ecological data derived from numerous biosystematic methods, including allozyme and nuclear and cpDNA analyses, topics of great importance for every plant biologist, such as sympatric and allopatric introgression, hybrid speciation and, last but not least, the genetic structure of hybrid populations in the hybrid zone and its relationships to microhabitat fluctuations, are discussed.

The following seven chapters address current research on hybridization and hybrid zones in animals. The theory about secondary, postglacial formation of hybrid zones between two subspecies of Chorthippus parallelus in the Pyrenees is very well documented in the paper by Hewitt. Two evolutionary important process - adaptation and speciation - are addressed in a report by Shaw et al. The authors have concentrated on detailed karyotypic

This content downloaded from 62.122.78.91 on Sat, 14 Jun 2014 18:18:00 PMAll use subject to JSTOR Terms and Conditions

Bookreviews 167

analysis and chromosomal changes to explain reproductive isolation that exists in the hybrid zone between Torresian and Moreton samples of Caledia captiva.

In the case study of hybrid zones between red- and yellow-schafted flickers (Colaptes auratus), one of the most abundant birds in North America, Moore and Price illustrate how selection and the genetic system interact to maintain the integrity of the taxonomic units in the hybrid zones. Using evidence from the hybrid zone, the evolution and mode of initial divergence - parapatric or allopatric - in neotropical Heliconius color pattern races are discussed in Chapter 9 (Mallet). To clarify the structure of hybrid zones where Bombina bombina and B. variegata meet, several transects in central Europe were investigated in detail by Szymura, using molecular methods such as allozyme and mitochondrial DNA analysis.

Patton in his review has concentrated on the issues of hybridization and hybrid zones in pocket gophers (Rodentia, Geomyidae) to elucidate the species boundaries between geographically differentiated units (be these recognized at various taxonomic levels). The report by Searle "Chromosomal hybrid zones in Eutherian Mammals" starts with excellent description of numerous types of chromosomal variants. Showing the various types of karyotypic variation in hybrid zones of examined small mammals, Searle discusses several important topics such as staggered hybrid zones and radiation, and chromosomal hybrid zones as genetic barriers or speciation and chromosomal evolution.

This book gives a comprehensive overview of the interesting field of hybridization and its taxonomic, ecological and evolutionary implications. It presents good examples from hybrid zone research both in plants and animals. It can be highly recommended to all with an interest in the various fields of hybridization and introgression and should be in all zoological and botanical libraries.

Jitka 6t6pAnkova

V. Ahmadjian: THE LICHEN SYMBIOSIS; John Wiley & Sons, Inc., New York, 1993, 250 pp. Price GBP 58.-, ISBN 0-471-57885-1

Lichen symbiosis, revealed in 1869 by Schwendener, still remains an enigmatic aspect of life. Vernon Ahmadjian devoted many years of research to the interactions of alga and fungus in a lichen thallus. A great achievement was the artificial resynthesis of Cladonia cristatella (an excellent colour photograph is in the frontispiece). In 1967 Ahmadjian summarized existing knowledge and especially his own experience in an earlier version of The Lichen Symbiosis, which stimulated research into cultivation of lichen bionts. Recently a resynthesis of cyanolichens has been achieved with soil cultures and thallus fragments. Likewise, environmental experiments have yielded interesting and valuable data. Progress in physiology, ontogenesis and molecular biology concerning lichen symbiosis is well documented and summarized in a new book with the same title.

The introductory chapter gives the basic facts on the nature of lichens and discusses the definition of a lichen. The next two chapters are devoted to the ultrastructure and physiology of both individual symbionts, mycobiont and photobiont. Special attention is focussed on the isolation and growth of the mycobiont in culture and on problems of taxonomy and other controversial aspects of Trebouxia, the most common lichen photobiont. The following three chapters are the core of the book, dealing with the interactions of the symbionts. Artificial synthesis is the key to a better understanding of lichen symbiosis. The substantial phases of artificial resynthesis studies are summarized: recognition between bionts, their specificity and selectivity, early thallus development and fruiting of the mycobiont. Special attention is paid to the chemistry and ultrastructure of synthetic lichens. Physiological interrelationships and carbohydrate movement are fundamental aspects of lichen symbiosis, but are not yet completely understood. However, it appears obvious that the bionts have co-evolved a sophisticated system of nutrient exchange and movement that involves feedback controls and adaptive responses to specific habitats. Physiological buffering is a concept which explains the survival of lichens under environmental stress and the carbohydrate pool plays an important role in the effects of drying-and-wetting cycles. The factors influencing growth and nitrogen fixation are also discussed. Another special feature of lichens is their sensitivity to air pollution which started a boom of bioindication studies two decades ago and consequently. Lichen sensitivity studies and the effects of various pollutants are reviewed. The last chapter is devoted to molecular

This content downloaded from 62.122.78.91 on Sat, 14 Jun 2014 18:18:00 PMAll use subject to JSTOR Terms and Conditions