Professor Armen Takhtajan, a giant among botanists, has spent a lifetime in the service of his science and of humanity. As a thoroughgoing internationalist, he promoted close relationships between botanists and people of all nations through the most difficult times imaginable, and succeeded with his strong and persistent personal warmth. He also has stood for excellent modern science throughout this life, and taught hundreds of students to appreciate the highest values of civilization whatever their particular pursuits or views, or the problems they encountered.
Takhtajan has made multiple contributions to our understanding of plant evolution, particularly concerning angiosperms and their classification. As early as 1943, in his paper "Correlations of Ontogenesis and Phylogenesis in Higher Plants," he put forward a theory of the macroevolution of many groups of plants through neoteny; he elaborated this theory in later publications. Takhtajan's ideas on macroevolution as a result of changes in developmental timing (heterochrony or heterobatmy) has been viewed favorably by a number of outstanding biologists, including Agnes Arber (in "The Natural Philosophy of Plant Form", 1950) and Stephen Gould (in "Ontogeny and Phylogeny", 1977). His principal ideas were that the origin of herbaceous angio-sperms was the result of neoteny and that the origin of some arborescent forms was secondary. He also offered hypotheses about the way in which monocot leaves, with their characteristic parallel venation, and discussed well the patterns involved in the origin of stomata. Takhtajan produced a novel classification for the structural types of gynoecium and of their placentation. He also wrote on the evolution of inflorescences, the evolution of pollen grains, and the evolutionary classification of fruit types. His theory of the evolution of inflorescences, in which he postulated that a leafy cyme was the original type, was accepted by Stebbins ("Flowering Plants, Evolution Above the Species Level," 1974: 263). One of the his most important contributions was the idea that the origin and evolution of male and female gametophytes of the angio-sperms came about through evolutionary changes in developmental timing accompanied by drastic modifications of the ontogenetic processes involved.
Takhtajan's most important achievement has been the development of his phylo-genetic system of the flowering plants, a system that has greatly influenced all other recent systems of classification; in turn, Takhtajan was inspired by Hans Hallier's earlier theories. He published a preliminary phyletic diagram of the orders of angio-sperms as early as in 1942, and this diagram was mentioned by Gundersen in his "Families of Dicotyledons" (1950). Later in his large book, "A System and Phylogeny of the Flowering Plants" (1966) and in his "Systema Magnoliophytorum" (1987), both in Russian, as well as in "Diversity and Classification of Flowering Plants" (1997), in English, Takhtajan provided a detailed exposition of his system as well as the reasons for his delimitation and arrangement of families and orders. One of his main innovations was the subdivision of both the dicots and monocots into subclasses, which was widely accepted as a major advance in angiosperm classification and introduced into some textbooks, including the last edition of Strasburger's "Lehrbuch der Botanik".
Takhtajan's system of classification is a synthetic, integrated one based on all available data, including recent studies in embryology, palynology, comparative anatomy, cytology, phytochemistry, and molecular data, as well as on cladistic analyses of many taxa. This new book, as well as "Diversity and Classification of Flowering Plants", includes also intrafamilial classification (subfamilies and tribes).
Armen Takhtajan has worked for many years at the Komarov Botanical Institute, St. Petersburg, Russia (LE), where he had access to its great herbarium collections and library. He used these rich resources to supplement his field experience in many regions in the world. As a result of his studies and the observations he was able to make during the course of his travels, he prepared a book entitled "Floristic Regions of the World," in which he presented not only floristic divisions for the whole world, but also listed endemic families and genera and provided examples of endemic species for each province.
At the present, the classification of angiosperm families and our ideas of their relationships are moving forward rapidly; current studies have led and are leading to many significant changes in our interpretations, largely following the important clues about relationship that have come from molecular comparisons between taxa. Because of the numerous examples of parallelism and evolutionary convergence among the angiosperms and their individual structures, some of the ideas gained by earlier, often meticulous analyses of morphological, anatomical, and even chemical features. The classification presented in the current book should be understood as a summary of a life's study of plants and the system that his insights support - the work of a very great botanist that takes into account not only his own meticulous studies but as much of the contemporary information as he was able to assimilate and take into account. Although future classifications will clearly go beyond the stage of development represented here, it is important to be able to benefit from Armen Takhtajan's insights into the features of flowering plants and the ways in which the suites of characteristics they present can be viewed in an evolutionary context.
Takhtajan is a botanist of the 20th century, and the views developed from his vast experience - he is nearly 100 years of age - richly deserve publication. Younger research workers and students will appreciate the opportunity to be informed of Armen Takhtajan's ideas, and to be acquainted with the wide ranging data on where they are based. This book naturally draws extensively on the rich Russian literature in the field of plant classification, and many readers will find ideas expressed that are of interest to them. The new insights and ideas in the book likewise will inspire new levels of thinking about the relationships between the families of angiosperms and their evolutionary history, including the convergent and parallel evolution of particular features.
Peter Stevens, one of the reviewers, has pointed out that additional evidence has accumulated regarding the relationships of many angiosperm families, and that comparisons of their DNA have revealed unsuspected similarities. Armen Takhtajan has taken into consideration some, but not all, of this evidence, and future treatments will result in major revisions of some of the concepts presented here. Importantly, he brings to our attention the pertinent Russian botanical literature, which is poorly known in the West. This book presents challenging new ideas and insights clearly, and it is very important to publish for its demonstrated value as the final work of a great scientist, representing the culmination of his experience and study.
It is also important to mention that this book summarizes the ideas and understanding of a lifetime of investigation and thought by one of the most able and influential botanists of our time. Considering his age, it will probably be the last one. - Peter H. Raven, President and Director, Missouri Botanical Garden, St. Louis, Missouri, USA.
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