The Evolution of Phylogenetic Systematics

The Evolution of Phylogenetic Systematics

SPECIES AND SYSTEMATICS

www.ucpress.edu/go/spsy

The Species and Systematics series will investigate fundamental and practical aspects of systematics and taxonomy in a series of comprehensive volumes aimed at students and researchers in systematic biology and in the history and philosophy of biology. The book series will examine the role of descriptive taxonomy, its fusion with cyber-infrastructure, its future within biodiversity studies, and its importance as an empirical science. The philosophical consequences of classification, as well as its history, will be among the themes explored by this series, including systematic methods, empirical studies of taxonomic groups, the history of homology, and its significance in molecular systematics.

Editor in Chief: Malte C. Ebach (University of New South Wales, Australia)

Editorial Board

Sandra Carlson (University of California, Davis, USA)

Marcelo R. de Carvalho (University of São Paulo, Brazil)

Darren Curnoe (University of New South Wales, Australia)

Christina Flann (Netherlands Centre for Biodiversity Naturalis, The Netherlands)

Anthony C. Gill (University of Sydney, Australia)

Lynne R. Parenti (Smithsonian Institution, USA)

Olivier Rieppel (The Field Museum, Chicago, USA)

John S. Wilkins (University of Sydney, Australia)

Kipling Will (University of California, Berkeley, USA)

David M. Williams (The Natural History Museum, London, UK)

René Zaragüeta i Bagils (University of Paris 6, France)

The Evolution of

Phylogenetic Systematics

EDITED BY

Andrew Hamilton

UNIVERSITY OF CALIFORNIA PRESS

Berkeley•Los Angeles•London

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Species and Systematics, Vol. 5

For online version, see www.ucpress.edu.

University of California Press

Berkeley and Los Angeles, California

University of California Press, Ltd.

London, England

© 2014 by The Regents of the University of California

Library of Congress Cataloging-in-Publication Data

The evolution of phylogenetic systematics / edited by Andrew Hamilton.

pages cm — (Species and systematics ; v. 5)

Includes bibliographical references and index.

ISBN 978-0-520-27658-1 (cloth : alk. paper) —

ISBN 978-0-520-95675-9 (ebook)

1. Cladistic analysis.2. Biology—Classification—Philosophy.I. Hamilton, Andrew, 1972-

QH83.E962014

578.01’2—dc232013021973

Manufactured in the United States of America

23  22  21  20  19  18  17  16  15  14

10  9  8  7  6  5  4  3  2  1

The paper used in this publication meets the minimum requirements of ANSI/NISO Z39.48–1992 (R 2002) (Permanence of Paper).

Cover illustration: Chart of Evolution (1937) by Borgny Bay, Paleontological Museum, University of Oslo. Photo by Colin Purrington, courtesy of the Gould Library, Carleton College.

Contents

List of Contributors

Introduction

Andrew Hamilton

PART ONE. HISTORICAL FOUNDATIONS

1Reflections on the History of Systematics

Robert E. Kohler

2Willi Hennig’s Part in the History of Systematics

Michael Schmitt

3Homology as a Bridge between Evolutionary Morphology, Developmental Evolution, and Phylogenetic Systematics

Manfred D. Laubichler

PART TWO. CONCEPTUAL FOUNDATIONS

4Historical and Conceptual Perspectives on Modern Systematics: Groups, Ranks, and the Phylogenetic Turn

Andrew Hamilton

5The Early Cladogenesis of Cladistics

Olivier Rieppel

6Cladistics at an Earlier Time

Gareth Nelson

7Patterson’s Curse, Molecular Homology, and the Data Matrix

David M. Williams and Malte C. Ebach

8History and Theory in the Development of Phylogenetics in Botany

Brent D. Mishler

PART THREE. TECHNOLOGY, CONCEPTS, AND PRACTICE

9Well-Structured Biology: Numerical Taxonomy’s Epistemic Vision for Systematics

Beckett Sterner

10A Comparison of Alternative Form-Characterization: Approaches to the Automated Identification of Biological Species

Norman MacLeod

11The New Systematics, the New Taxonomy, and the Future of Biodiversity Studies

Quentin Wheeler and Andrew Hamilton

Index

Contributors

Malte C. Ebach

University of New South Wales

mcebach@unsw.edu.au

Andrew Hamilton

University of Houston

ahamilton@uh.edu

Robert E. Kohler

University of Pennsylvania

rkohler@sas.upenn.edu

Manfred D. Laubichler

Arizona State University

manfred.laubichler@asu.edu

Norman MacLeod

Natural History Museum, London

University College London

n.macleod@nhm.ac.uk

Brent D. Mishler

University of California, Berkeley

bmishler@berkeley.edu

Gareth Nelson

University of Melbourne

garethn@unimelb.edu.au

Olivier Rieppel

The Field Museum

orieppel@fieldmuseum.org

Michael Schmitt

Ernst-Moritz-Arndt-Universitaet

michael.schmitt@uni-greifswald.de

Beckett Sterner

University of Chicago

bsterner@uchicago.edu

Quentin Wheeler

Arizona State University

quentin.wheeler@asu.edu

David Williams

Natural History Museum, London

d.m.williams@nhm.ac.uk

Introduction

ANDREW HAMILTON

TRENDS AND TRADITIONS IN PHYLOGENETIC SYSTEMATICS

In spring 2006 I met with the entomologist and systematic theorist Quentin Wheeler to discuss topics of common interest: species concepts, methodology in systematics, the recent history of phylogenetic classification, and biodiversity from a systematics perspective. The conversation turned out to have a surprising twist. Quentin was founding a new research center at Arizona State University—the International Institute for Species Exploration (IISE)—that would have a focus on the history and philosophy of systematics. I jumped at the chance to direct this part of the Institute’s program because I saw that there was plenty of work to be done that would best be accomplished through the collaborative efforts of systematists, historians, and philosophers.

With help from Manfred Laubichler, I set about recruiting scholars from several disciplines to participate in a workshop to help define and articulate the agenda for the history and philosophy of systematics at the IISE as well as in my own work. Topics of discussion in the workshop ranged from instrumentalism in contemporary systematics to the relationships between homology and monophyly, Willi Hennig’s theoretical commitments, and on to how the history of recent and highly contested biology should be most productively pursued.

No attempt has been made to reproduce the breadth of the workshop discussions here. Rather, I have narrowed the scope considerably by including chapters that address issues of historical or conceptual concern to students and practitioners of phylogenetic systematics. The workshop confirmed that there is a lack of historical work on Hennig and his immediate forerunners and made it clear that for two decades before and after World War II, systematics developed more or less independently in two contexts. Put much too simply, the Anglo-American context in which J.S. Huxley, Ernst Mayr, G.G. Simpson, and other proponents of evolutionary taxonomy worked was focused on the modern synthesis and on making systematics an important part of evolutionary biology. As Huxley put it in his 1940 volume, The New Systematics, fundamentally, the problem of systematics, regarded as a general branch of biology, is that of detecting evolution at work (2). The synthesis and the contributions of its architects have been well studied from both historical and conceptual perspectives.

Phylogenetic systematics—or at least the branch of it that became known in the late 1960s and early 1970s as cladistics—developed in quite a different context from that of evolutionary taxonomy and has been much less studied. A few commentators (Hull 1988; Donoghue and Kadereit 1992; Bowler 1996; Rieppel 2006) have noted that Walter Zimmermann and Willi Hennig, founders of the cladistic approach, both reacted strongly against the resurgence of idealistic morphology in the German-speaking world. The sense in which the new approach they developed came out of this context has not been well explored, though there is an emerging literature. If the new systematics (which included evolutionary taxonomy) was a self-conscious attempt to save taxonomy from being overlooked in favor of an evolutionary theory that included molecular genetics as a preeminent component, to what, exactly, was cladistics a response? What set of conceptual, practical, and empirical problems were Hennig and his collaborators, forebears, and followers trying to solve, and how were they different from those faced by scientists working in the context of the synthesis? Several of the chapters in this volume address these questions directly.

In addition to historical questions, there are closely related conceptual ones: much of what was under discussion in both camps was methodological, epistemological, and ontological. In this last category were concerns about species, the process(es) of speciation, and what kind(s) of groups ought to be regarded as natural and therefore appropriate for study by systematists. In the methodological and epistemological categories were debates about reconstructing phylogenies, homologies and what they mean, the information content of systematic claims, and the best basis for systematics, including the question of whether systematics ought to be phylogenetic at all. It turns out, not surprisingly, that understanding these conceptual debates in detail requires further splitting than that between German-speaking cladists and English-speaking synthesists provides: zoologists and botanists took up these issues in very different ways, even when they were working in the same national context. There were points of shared concern—evolutionary reticulation chief among them—but the differences in the way species were understood and how relationships between taxa were conceived and represented point to a need for a richer understanding of the conceptual structures in use in the decades leading up to the wide-scale embracing of phylogenetic systematics as we now know it.

The meaningful debates, of course, did not end with the publication of Hennig’s work in English or with the development of his ideas in his few published interactions with evolutionary taxonomists. In selecting and preparing the chapters for this volume, it became clear that important parts of the more recent history of phylogenetic systematics have not been sufficiently treated. Recent work by systematists and biogeographers who have been exploring their own history have opened new avenues of inquiry (Williams and Knapp 2010). As several authors in this volume point out, many of the systematists who were important in advancing Hennig’s ideas in the United States and the United Kingdom first learned of Hennig through the dipterist and biogeographer Lars Brundin. There is a case to be made, however, that though Brundin and Hennig were treated as having the same view by their critics—see, for instance, Darlington’s (1970) response to Brundin’s (1966) monograph—their views and the views of those that followed diverged in subtle ways that may prove important for understanding and explaining the trajectories cladistics took in the late 1970s and through the 1980s and even today. Several contributions in these pages speak to Brundin’s impact and its ramifications for early adopters of the phylogenetic approach to systematics.

Wherever the splitting points between schools of phylogenetic thought are to be located, it is clear that the debates between them are overtly conceptual, even philosophical, in ways that are fairly rare in the sciences. It may be going too far to say, with the microbiologist Susan Perkins (2011, 895), that cladists are often seen as obsessed with the philosophical underpinnings of science. As the chapters in this volume show, however, it certainly is the case that Hennig paid serious attention to the philosophical literature he took to be relevant to his work and that contemporary disagreements about ranking, species, and the relative importance of pattern and process are rooted in sophisticated, though sometimes conflicting, understandings of the appropriate nature of science. One reason for putting this volume together is that in this case, historical and conceptual foundations are tied together so closely that it is difficult to understand either without the other. And it is difficult to understand recent developments in systematics and how to evaluate them without both.

This volume would have been incomplete without a look at systematics through the lens of contemporary issues in technology, biodiversity, institutions, and practice. In systematics there is much to be said about the changing relationships between field biology, the laboratory, collections, and the use of computers and how all these articulate with concepts about what is collected, curated, and displayed and for what purpose. Here these broader issues are addressed in several ways, including one chapter that contains a nuanced study of the history of systematics in the United States and three chapters that explore the ways computing technology has contributed to, built on, and rendered complex the relationships between systematic theory and practice. As with many other fields of science, technology has made a dramatic impact in systematics. Unlike some other fields, however, technology has changed the way some people think about the basic structure of both the day-to-day work and the theoretical underpinnings of the discipline.

THE STRUCTURE OF THIS VOLUME

This volume is not so much a collection of the papers given at the 2008 IISE meeting as it is an attempt to bring the conceptual, historical, and social foundations of modern phylogenetic systematics into sharper relief and to offer a springboard for further work in the area. As Robert Kohler points out in his contribution, systematics may be the biological science that is least well studied by historians, yet it is of overarching interest because of its connections to biodiversity, collections, the rise of natural history museums, and field studies and the important part it has played in the development of contemporary biology, especially the biodiversity sciences. In addition, there is this: systematics is both the site of a recent genuine revolution in fundamental concepts and an arena of ongoing debate and discussion. What is as stake in the near future is the way we should understand classification, especially ranking, and how the objects of systematics (species and clades) inform our view of the biological world, its study, and its management.

Contributors to this volume come from several disciplines but have not separated historical investigations from conceptual, social, or biological ones. Neither have they taken pains to discuss only the past, present, or future. Most chapters discuss more than one aspect of systematics from more than one disciplinary or temporal perspective. Several threads run through the volume. One of these is the topic of how systematics became phylogenetic. Here the how points not only to the necessary conceptual changes—and therefore to Willi Hennig—but also to the necessary social and practical innovations. Another thread concerns what, exactly, is being studied and whether and why phylogenetics is the best or most appropriate approach to understanding and bounding biological objects. A third thread addresses the set of tools and methods for doing the work: from simple nets for collecting insects to the sophisticated computer-based imaging and bioinformatics infrastructure described in the chapters at the end of the volume. A fourth thread takes a phylogenetic approach to phylogenetic systematics itself, trying to locate the points in history at which systematics split into multiple lineages, along with the reasons for these branchings.

I have organized these and other threads in three parts. The first, Historical Foundations, both locates modern systematics in its larger context and acknowledges the importance of Willi Hennig for systematics in the second half of the twentieth century and into the twenty-first. It also, first implicitly and then explicitly, addresses the role of changes in technology as they bear on conceptions of theory and practice in systematics. Part 2, Conceptual Foundations, does two jobs at once. In addition to tracing the changes described in part 1 as they are reflected in conceptual debates and discussions about basic notions in systematics, part 2 includes detailed first-person histories that throw light on how and why some systematists both understood and came to embrace the Hennigian approach. The final part, Technology, Concepts, and Practice, describes technologically enabled approaches to systematics, along with their justifications and limitations.

Because the history of systematics and its conceptual foundations are intertwined, the divisions in this book are largely artificial; they are intended to structure the reader’s approach to the volume rather than to insist on an intellectual division of labor between scientists, historians, and philosophers or between past, present, and future. One major motivation for the volume is that the history of systematics has been understudied and that since systematics informs so much of the rest of biology, it will become increasingly important to understand what systematics is, how its concepts developed and what they mean, and where systematics might be going.

Part 1 begins with Rob Kohler’s extended look at the history of natural history in the United States in the nineteenth and twentieth centuries. Kohler reminds those of us who spend most of our time working with concepts or archived volumes that systematics begins and ends with natural history collections. He argues compellingly that a comparative history of systematics will be necessary if we are to understand the bigger picture, and he frames some questions that can structure such an inquiry. Kohler’s chapter is a challenge to the community as much it is a contribution to knowledge about collections and their use. He points to much more good work that needs doing: what is collected, by whom, to what end, and for what reward varies quite a lot with place, time, and other factors. Understanding collections in detail puts us far along the path to being able to see systematics and its related disciplines in greater detail.

Michael Schmitt, who has emerged in recent years as Hennig’s foremost biographer, acquaints readers with Hennig the man, and also with Hennig the founder of modern phylogenetic systematics. Those who are unfamiliar with Hennig’s work will find in chapter 2 a concise introduction to several of the most important features of his thinking, including the way he refined and used Ernst Haeckel’s notion of monophyly, as well as his own use of the concept of synapomorphy and how his thinking about parent-offspring relations led him to controversial conclusions (including the so-called dichotomy rule) about the relationship between stem species and the entities to which they give rise. Schmitt also points to some interesting omissions in Hennig’s work, including the lack of a method for determining character polarity—a crucially important part of a systematics that is based on knowledge of, or at least on hypotheses about, which character states are primitive and which are evolutionarily derived.

In chapter 3 Manfred Laubichler discusses some important conceptual shifts in ideas about homology and phylogeny in the German-speaking context in the early twentieth century. As Laubichler points out, homology is a central concept for all of comparative biology, and it is at the very core of phylogenetic systematics and attempts to understand phenotypic evolution. Not surprisingly, given the kinds of disagreements that characterized biology over the course of the late nineteeth and early twentieth century, homology has been a highly contested notion, and its history provides a window on these disagreements. Laubichler draws out a distinction first made by Hans Spemann in 1915 between a historical notion of homology and a developmental one, arguing that the developmental framing funded some of the conceptual innovations in phylogenetic systematics made by Walter Zimmermann (an early influence on Hennig) and by Hennig, but also reinforced a long-standing and ongoing confusion about the units of phenotypic evolution and phenotypic transformation. Understanding this confusion, Laubichler argues, makes the contours of some of the debates at the intersection between cladistics and developmental evolution clearer.

Part 2 begins with a transitional chapter, chapter 4, which serves to shift the focus slightly, but only slightly, from history to conceptual foundations by examining Hennig’s use of what later became known as the individuality thesis in the context of his work. In this chapter I explore the rise of phylogenetic systematics from Darwin to Hennig, detailing some important concerns that were raised in the first half of the twentieth century about phylogenetic approaches to systematics. These challenges came from German-speaking scientists working in the tradition of idealistic morphology, and also from English and American scientists who were trying to reconcile evolution with classification. Both groups had the problem, as Olaf Breidbach (2003, 182) has pointed out, that at the start of the 20th century there was no definitive argument to secure phylogenetic systematics. I argue that first Zimmermann and then Hennig addressed critics by way of a sophisticated set of ontological arguments that had consequences for how systematists should understand the basis of their science as well as what sorts of things they were studying. On this analysis, the long-standing questions of how to group organisms into species and species into clades have answers that are well informed by theory, but taxonomic ranking remains an important and ongoing problem.

Chapter 5, by Olivier Rieppel, continues a focus on Hennig’s ontology but in a wider context. Rieppel provides important details about how Hennig developed some of the more theoretical aspects of phylogenetic systematics, with a special focus on Hennig’s philosophically informed thinking about individuals and how he understood their logical and structural relations to each other. Reippel contrasts this analysis of the ontological foundations for Hennig’s work with the ontology that came just a little later, and in so doing provides the volume’s first real introduction to the pivotal role played by Lars Brundin in the adoption of Hennigian ideas.

Rieppel argues that Hennig’s ideas were not just adopted but also adapted, even as early as Brundin’s 1966 introduction of Hennig to English-speaking systematists. According to Rieppel, a difference in philosophical backgrounds between the Anglo-American receivers of Hennig’s work and its German foundations contributed to a split between theorists regarding how to understand some foundational ideas in phylogenetic systematics in the late 1960s through the 1970s and 1980s, including its relationship to evolution. It is as a part of this conversation that we meet some of the first and historically most important champions of cladistics, among them Colin Patterson and Gareth Nelson.

In a chapter that is partly first-person history and partly an exploration of the written first-person accounts of others, Nelson explores both what happened as he and others discovered Hennig through Brundin and how they understood the conceptual changes that the phylogenetic approach brought with it. Nelson’s piece recounts his own discovery of Brundin’s monograph in the reading room of the Swedish Museum of Natural History in fall 1966, as well as Patterson’s conversion (Patterson’s term) to Hennig’s ideas after reading Brundin.

In addition to offering further documentation of the importance of Brundin to the spread of phylogenetic systematics, Nelson’s chapter points to the role paleontologists played in the adoption of some of Hennig’s ideas, especially his conception of systematics as the search for sister groups. The extent to which paleontology is a crucial part of the story of the rise of cladistics has not been widely appreciated. Nelson’s emphasis on the differences in content between the 1967 Nobel Symposium on Lower Vertebrate Phylogeny and the 1972 Linnean Society of London meeting in honor of the paleontologists Erik Stensiö and Erik Jarvik provides strong evidence of a major shift toward phylogenetics among those who worked on fossil fishes.

Chapter 7, by David M. Williams and Malte C. Ebach, addresses social and scientific aspects of the branching of cladistics through the lens of Colin Patterson’s thinking about the relationship between systematics and evolution. In November 1981 Patterson gave an intentionally provocative talk on this topic at the American Museum of Natural History. The incident became famous or notorious, depending on one’s perspective, in part because it was surreptitiously recorded and then circulated among creationists, many of whom took it as evidence that even senior biologists doubt the truth, viability, or usefulness of evolutionary theory.

The relationship between systematics and evolution, as several chapters in this volume show, is complex. Through a look at Patterson’s work and thought, Williams and Ebach illuminate not only the 1981 talk but also something of the character of biologists’ attempts in the early 1980s to understand cladistics in relation to systematic biology generally. These efforts were complicated by the rise of molecular and algorithmic methods for doing phylogenetics in the mid-1960s and unfriendly arguments among cladists about which sets of concepts and methods should be adopted.

Williams and Ebach argue that reading Patterson as a creationist is an understandable tactic for creationists but little more than a bludgeon for his fellow systematists. As they understand Patterson, he thought cladistics had branched into two schools by the early 1980s because of differences in the understanding of key concepts—especially phylogenetic relationships and homology—as well as methods. Patterson was an early critic of molecular approaches to systematics partly because he thought that using algorithms to analyze sequence data does not accomplish the same task as using morphology to discover phylogenetic relationships. He held that morphological and molecular homologies are not the same thing: molecular homologies, he thought, are missing the direct evidence of character transformation that one can find in morphology. As Williams and Ebach show, this view was informed by a particular understanding of homologies and their relation to characters and to ontogeny, rather than by allegiance to creationism.

Williams and Ebach go a step further. Having offered a detailed analysis of Patterson’s thinking as a means of making his discussion of creationism clearer, they go on to examine certain rhetorical practices among systematists from the 1980s up to today, especially as they relate to dismissals of Patterson’s concerns about molecular systematics on the grounds that he was a creationist. In so doing, they offer insights into the interplay between what they call the scientific and political content of the debates over concepts and methods that are ongoing in systematics.

In the final chapter of part 2, Brent Mishler offers what is partly first-person history. He takes a historical view as a means of offering suggestions for continued integration of theory and practice in botany and zoology. In so doing, he begins to address an embarrassing lacuna in the literature, pointing out that botany and zoology have importantly different histories, approaches, and conceptual structures for phylogenetic systematics—or that at least they did until fairly recently. As he notes, botany and zoology came to phylogenetics from quite different directions, with most botanists standing outside of the modern evolutionary synthesis partly because of their dislike of the biological species concept and partly because their ways of working were (and are) different from systematists who work on animals.

Mishler argues that the practice of assembling and publishing floras has much to do with these differences, and in particular, that the way botanists have represented relationships among groups in their floras has worked against a phylogenetic understanding of those groups. While the value of Mishler’s chapter lies in part in calling attention to the differences between botany and zoology to which historians and philosophers have not paid enough attention, there is also value in his first-person account of the development of phylogenetic systematics in botany since the 1970s; he gives future historians something to push against as they try to make sense of the differences he describes.

Part 3 addresses the changes technology has brought and is bringing to systematics. The first chapter, by Beckett Sterner, is transitional both in the sense that it is historical in nature while the other two chapters in part 3 are forward-looking and in the sense that it shows the importance of computers in the way systematics was conceptualized in the twentieth century.

Drawing out a point of Kohler’s—that systematics attempts to get at nature’s inner workings and was never about mere cataloging—Sterner explores the ways the use of computers changed some systematists’ approach to nature in the mid-twentieth century. Focusing on the extreme and therefore revealing case of numerical taxonomy (introduced in Nelson’s chapter), Sterner traces the attempts of Robert Sokal and Peter Sneath to remake systematics according to a method of measurement and analysis that could only be accomplished effectively by machines. Sterner treats this episode as a case study of the reorganization of classificatory work and in so doing offers the kind of information about the relationships between methodologies, concepts, and ways of working that will be necessary if we are to move toward Kohler’s bigger picture. As Sterner points out, numerical taxonomy was not an old approach using new tools but a conscious and concerted reinterpretation of the world and how it might best be described and categorized.

This case is important not only for understanding the relationship between new technologies and the work of science but also because many of the numerical taxonomists’ innovations have been adapted to new purposes in contemporary systematics, especially molecular systematics. Sterner’s chapter also shows just how complex the recent history of systematics is. The main thrust of chapter 4 is that phylogenetic systematics in its modern form was born from conceptual shifts that were driven partly by a rejection of idealistic morphology and partly by shifts in ontology. Numerical taxonomy had none of these concerns. Indeed, its framers wanted it to be theory-free, a stance hardly imaginable without the use of computers for data analysis.

Chapter 10, by Norman MacLeod, marks a turn in this volume toward attention to new tools for systematists. MacLeod’s work on computer imaging systems is motivated in part by two studies showing that humans—including taxon experts—are not as good at consistently and correctly identifying biological species as one might have thought: human taxonomists do well to offer identifications that are consistent with other human taxonomists 70 percent of the time. MacLeod and his coworkers are exploring several image- and computer-based methods for identifying species (and other biological objects), all of which performed better than human taxonomists in the set of tests undertaken so far on several species of foraminifers.

This kind of automation goes right to the heart of issues about what twenty-first-century systematics will look like in terms of its social and intellectual organization. And it also has the capacity to reveal—through an analysis of the modeling and computer-learning assumptions built into image-analysis software—the conceptual assumptions systematists make about the edges and boundaries of species as read from their morphology.

The final chapter, chapter 11, continues the discussion of computer-based imaging as a tool for systematic analysis, with a focus on why an emphasis on comparative morphology—digitally captured—makes sense in an age of molecular evolution and bar code–based analyses of biodiversity. Quentin Wheeler and I provide a detailed look at the epistemology of phylogenetic analysis, arguing that the morphology-based description of species is the crucial first step in a rigorous process of understanding new species, their geographies, functions, and places on the phylogenetic tree. Analyses of gene and protein sequences can be helpful as we try to understand new findings and reconceptualize old ones, but Wheeler and Hamilton echo some of the discussion in Williams and Ebach’s chapter by arguing that molecular approaches are best understood as morphology writ small. As we move toward a systematics based more extensively in bioinformatics, they argue, we need to find new ways to capture morphology digitally and make it widely available for just the kind of analyses that are presently carried out. This will accelerate the pace of what Wheeler has long called species exploration while being faithful to the epistemic standards of phylogenetic systematics. This shift toward cyber-enabled taxonomy, they note, has important implications for how systematists do their work, as well as for how others might consume it.

NEXT STEPS

Much has been said recently in the popular (McClain 2011) and professional (Pearson, Hamilton, and Erwin 2011) literatures about systematics and the challenges it now faces. Many are concerned that systematics is underfunded and undervalued, even as we find ourselves in the midst of an anthropogenic mass extinction. This volume does not address issues of the relationship between taxonomy and biodiversity directly, but it does provide historical and conceptual background that will be necessary as scholars move to understand the place of contemporary systematics among the other biodiversity sciences and their place in science and conservation policy.

It is often claimed, for instance, that understanding species conceptually is a sine qua non for comparative biodiversity studies. Several of the chapters in this volume argue implicitly against this view or at least call for a stronger defense of it than is usually offered. Do we need a species concept to establish biodiversity baselines if botanists and zoologists have very different ideas of what species are, and if it is true that tracking lineages rather than species is the best and most useful approach to understanding the evolutionary path of life on Earth? If our categories and units of analysis are importantly informed by professional practices, as they surely are, will it not be profitable to understand in detail what