A növények evolúciója és osztályozása (Evolution and Systematics of Plants). — By J. Podani

Here is a textbook on plant systematics for which, unfortunately, botanists who do not read Hungarian may wait in vain to see it translated into English, or indeed any other more widely spoken language. This is unfortunate, because the author, a professor in the Department of Plant Systematics, Ecology and Theoretical Biology at the Eötvös University in Budapest, Hungary is someone whose work deserves to be better known. To that end, he has published in English throughout his career, most notably an introduction to multivariate methods for biologists (Podani 2000) and a software package for multivariate analyses, Syn-Tax (Podani 2001). Since the time he was a graduate student in Canada, doing a second doctorate with Laszlo Orlóci, he has also published extensively on the use of tree diagrams to summarize relationships, whether in ecology or systematics (e.g. Podani 1989, 2009, 2017, 2013; Podani et al. 2001, 2009). This interest in classification, and in one of the principal tools for arriving at classifications, is manifest in his book on plant systematics. In this book, Podani asserts he has departed from the standard approaches to the subject by treating as plants “all organisms|$\ldots$|that are known to possess plastids of primary endosymbiotic origin” (Podani 2015). Additionally, he asserts the novelty of treating glaucophytes, red algae, and green plants in such a way that, “Linnaean ranks are almost completely abandoned, only genera and species, and therefore, binomial names are retained for practical, rather than theoretical reasons. The PhyloCode is followed for clades with published names and contents, for extinct and extant plants alike. Clades for which no proper PhyloCode names and definitions have been established are considered as node-based with names and contents corresponding to Linnaean taxa as revised by molecular phylogenetic methods.” (Podani 2015) The book consists of 11 chapters, the last of which being a summary in English, from which the description here is drawn. The first chapter is an exposition of the theory and methods underpinning the use of branching diagrams to represent classifications and evolutionary history. Podani is adamant that meaningful discussions of phylogeny and evolution that employ such diagrams must distinguish between the four different kinds of trees described in his 2013 paper (also in Podani 2017). These are distinguished according to whether time is explicitly depicted (diachronous, synchronous) or not (achronous, asynchronous), and whether the trees depict ancestor-descendant relationships (diachronous, achronous) or sister group relationships between organisms existing at the same time (synchronous, asynchronous). The second chapter provides a history of biological classification, including folk taxonomies, pre-Linnaean classifications, Linnaeus’ ranked classification, and the attempt to develop a rank-free, cladistic classification. Podani argues that this last is needed if classifications are to reflect underlying evolutionary processes, rather than providing nested pigeonholes into which the diversity of living things is to be merely sorted. Chapter 3 presents the endosymbiotic theory of the origin of photosynthetic eukaryotes (Archaeplastida), and is then followed by a series of chapters discussing the evolution of the successive clades of extant green plants and their fossil relatives: Viridiplantae (Chapter 4), Embryophyta, the conquest of the land, and the extant bryophytes (Chapter 5), Polysporangiophyta, the increasingly dominant sporophyte phase, and the development of vascular tissue (Chapter 6), Pan-Euphyllophyta (ferns and fern allies; Chapter 7), Pan-Spermatophyta (seed plants; Chapter 8), Pan-Angiospermae (Chapter 9), and the Eudicotyledoneae (Chapter 10). “The last figure of this book, Fig. 10.14 (p. 361) gives a summary of the cladistic relationships among crown clades of extant plants, with some gray edges added arbitrarily as symbols of extinct plant lineages. The classical gradist view of plant evolution, namely the transitional sequence given by “algae—bryophytes—pteridophytes—gymnosperms—angiosperms” is superimposed as a “ladder” upon the cladogram. This illustrates the simultaneity of two basic views on evolution—such that both of them can be perfectly explained by the six most important transitions: (i) the appearance of plastids as a result of endosymbiosis with cyanobacteria, (ii) the development of chlorophyll-b, giving rise to green plants, (iii) evolution of the embryo, (iv) dominance of the sporophyte, (v) the occurrence of the ovule and the seed and, finally, and (vi) the evolution of the fruit of flowering plants.” (Podani, 2015) Each of these chapters concludes with a device Podani has employed in his earlier book (2000), namely an imagined dialogue between professor and student concerning the topics just discussed. Possibly corny, or perhaps as Podani suggests, a more relaxed presentation that helps the reader digest the content. Finally, the book is accompanied by a CD-ROM (“Digital Herbarium”) containing over 5000 plant images, most of which were taken by Podani himself, and that illustrate the groups discussed in the book. Figure 10.14 from page 361 of Podani J. 2015. A növények evolúciója és osztályozása. (Evolution and Systematics of Plants). Labels are given as quoted from Chapter 11. Translation of Podani’s book seems unlikely, regardless of how desirable it might be. English-speaking (and -reading) systematists are fortunate, however, that so many of the ideas about tree diagrams that animate Podani’s book are ones he has already published in English, as noted above. This is important, because clarity of thought about how the history of organic evolution is communicated by means of these diagrams is critical not only for systematics and evolutionary biology, but also for our success in teaching new generations of students, and in communicating our science to the public at large. Especially to this latter end, it would be ideal if Podani’s ideas could also be married to insights from educational psychology concerning how evolution and phylogeny can best be communicated to the public (Lombrozo 2013). For example, Catley et al. (2012) point out how naïve readers interpret tree diagrams less successfully if they are presented in the ladderformat (like that used by Podani in his Fig. 10.14). Greater success follows from using the tree format (i.e. formatted as a dendrogram; see Podani 2017). In the botanical sphere, the authors of the highly thought of Plant Systematics—A Phylogenetic Approach (Judd et al. 2016) might consider adding Podani to their number so as to incorporate into their book the aspects of the present text that seem most needed, and least available in English-language textbooks.

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