Medina and Goffinet

Review Better shoes alone don’t get you to your destination Reviewed by 1 RAFAEL MEDINA BERNARD GOFFINET Department of Ecology and Evolutionary Biology, 75 North Eagleville Road, University of Connecticut, Storrs, CT 06269-3043, U.S.A. 1e-mail: [email protected] Zander, R. H. 2013. A Framework for Post-Phylogenetic Systematics. Zetetic Publications, St. Louis, MO 209 p. [ISBN 978-1492220404]. Price $ 19.98 (softcover). ¤¤¤ A major challenge of reconstructing evolutionary rela- work is summarized (Chapter 16). The book includes a tionships is how to deal with distinct branching orders in glossary, which is essential given that the author uses trees inferred from different datasets, in particular terms likely to be unfamiliar to most readers (self-nesting morphological and molecular datasets. Topological in- ladder, caulistic taxa, extended paraphyly, etc.). congruences should be fully reconcilable since these The most important criticism expressed by Zander, characters are drawn from the same organisms and hence and somehow his principal motivation, is phylogenetic should reflect the outcome of the same underlying structuralism, the belief that evolutionary patterns are macroevolutionary process. Current widely applied best described in terms of the properties and rules of fundamental theoretical principles severely constrain scientific constructs, specifically Hennigian cladograms. the interpretation of phylogenetic trees and constitute The cladistic logic for phylogenetic reconstruction perhaps the primary, most significant obstacle to unifying in terms of dichotomous sister-group relationships is inferences in an integrative evolutionary reconstruction. A commonly accepted as the legitimate way to represent critical evaluation of the applicability of these principles to the diversification of lineages through time, yet may in reflect natural processes has become necessary, consider- fact, on theoretical grounds alone, fail to reflect ing that large data sets are generated with relative ease, and evolutionary processes. To consider that internal nodes that topological conflict is likely to become the norm of a tree mark ancestors that are merely hypothetical, rather than the exception. Richard Zander, in his book A implies that speciation events are linked to the extinction Framework for Post-Phylogenetic Systematics,remindsus of the ancestral species (i.e., ‘‘pseudoextinction’’ in the that data and trees do not speak for themselves, and that it framework’s vocabulary). However, such assumption is we who provide the words to model the story about the seems to be only a formal convention that does not evolution of organisms. He challenges us to reflect on the match actual cases of speciation, where a ‘‘mother assumptions and constraints we have, often subcon- species’’ may remain virtually unchanged and paraphy- sciously, adopted. He outlines a new framework and, with letic after a budding speciation event. The consequences a provocative style, engages us in evaluating the principles of this assumption are extensively explored throughout we apply to the interpretation of trees inferred from data. Zander’s work, consequences that are unexpected and Zander starts with an analysis and critique of some of counterintuitive for those accustomed to think strictly in the widely applied methods of phylogenetics (Chapters 1 cladistic terms. Ultimately, a phylogenetic tree is still a and 2), setting the stage for the presentation of an graph that needs to be interpreted, a tool for evolution- innovative method for macroevolutionary reconstruction ary reconstruction, but not an evolutionary history itself. (Chapter 3), consisting of six fundamental ‘‘elements,’’ Similarly, incongruence between topologies inferred developed sequentially in Chapters 4–9. Further discus- from distinct data sets, in particular morphological and sion of aspects of systematic theory and method, such as molecular, should not be seen as hard incompatibilities the estimation of statistical support or the role of intuitive but rather ‘‘soft’’ incongruences as trees can potentially hypotheses (Chapters 10–15), follow before the frame- be reconciled given the proper interpretation. The Bryologist 117(4), pp. 431–433 Published online: November 11, 2014 0007-2745/14/$0.45/0 432 THE BRYOLOGIST 117(4): 2014 Another issue that receives special attention is the cladistic constraints on the interpretation and recon- need to recognize and formalize classical taxonomy, struction of evolutionary phenomena. If heterophylly which is based on comparative morphology, as a reliable may be an artifact resulting from Hennigian constraints source of scientific knowledge. The value of this on our interpretation of trees, then it is imperative to approach is typically downgraded on the implicit consider alternative processes underlying a given tree or argument that classical taxonomy is impregnated with set of trees that do not rely on pseudoextinction, and the subjective appreciation of traits by the expert. In hence explore the effect of recognizing persistent comparison, current phylogenetic methods based on ancestral taxa (i.e., named internal nodes) on the molecular data seem more robust and sophisticated, so reconstruction of the evolutionary history. We also find that in cases of topological incongruence, inferences very valuable the discussion on the scientific legitimacy from molecular data are systematically preferred, with of classical taxonomy and the search of a formalization the consequences that homology assumptions of mor- of abductive reasoning. No doubt, this book will phological characters are more readily rejected. Zander stimulate readers familiar with current phylogenetics argues that classical morphological analysis is, however, a to evaluate the foundations that are often implicitly, refined methodology based on abductive reasoning and unconditionally or subconsciously followed. usually subconscious heuristics that should generate On the other hand, we find that the argumentation robust working hypotheses. The lack of a formalized presented to highlight the value of morphological system- mathematical expression or statistical support may atics and, in fact, its imperative inclusion in modern account for the perception of classical taxonomy as systematics (a point we agree with), is constantly incompatible with the ‘‘hard sciences,’’ but as Zander impregnated with an excessive mistrust of molecular reminds us, molecular data are not free of homoplasy phylogenetics. Zander’s main concern is that the modus either, may yield ambiguous signal also, and typically operandi of most modern systematists faced with topolog- suffer from limited sampling of conspecific exemplars. ical incongruence between morphology and molecule Furthermore, and perhaps most importantly and indeed based trees is to force the interpretation of the evolution often acknowledged, gene trees may not be reliable of morphological traits onto the molecular topology, and proxies of macroevolutionary (species) trees, and should hence to readily accept homoplasy in the morphological be regarded primarily as a graphic depiction of the traits, or to merge morphologically distinct lineages on the properties of a dataset, rather than of the evolutionary basis of recognizing only monophyletic lineages. Zander’s process directly. framework, however, is not free of a similar bias, since it With the aim of integrating the valuable sources of allows one to explain virtually all incongruences between information provided by classical taxonomy and molec- classical taxonomy and molecular trees in terms of artifacts ular phylogenetics, Zander proposes a method (the caused by cladistic structuralism, forcing the interpretation ‘‘framework’’ itself) consisting of the following steps: a of the molecular tree onto that inferred from morpholog- taxonomic treatment based on morphological analysis, ical traits (as if it were itself always an unequivocal exercise). followed by the generation of a natural key based on the We agree with the call for a pluralistic systematics, but do morphological treatment, then the incorporation of not endorse the approach to build evolutionary recon- molecular systematics analyses, and finally the optimi- struction on the immutable foundation provided by the zation and consolidation of both sources of information expert taxonomist. (including incipient mechanisms to integrate support Of course, the accumulated study of specimens values combining posterior probabilities and coarse leading to the elaboration of species concepts and priors). The goal is to reach a representation of the relationships is essential to the modern systematic evolutionary process that is not constrained by cladistic endeavor, but regardless of the time devoted to alpha structuralism, combines evidence from different sources taxonomy or the experience of the taxonomic authority, and allows for the recognition of paraphyletic taxa. As species concepts and relationships are only hypotheses. part of his framework, Zander proposes alternatives to The strength of these is highly dependent on the the traditional cladogram, to the Newick formula, and underlying assumptions one makes, and (here we agree the artificial dichotomous key, to integrate and reflect with Zander) one should be aware and remember these the processes that shape evolutionary histories. and assess their basis before endorsing or rejecting any The concerns expressed by Zander are not new—as one hypothesis. It is not pluralism to force all

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