The question posed by David Baum in the title of his book review, "Does the future of systematics really rest on the legacy of one mid-20th-Century German entomologist?" is deliberate distortion of our book's title, :The future of phylogenetic systematics: the legacy of Willi Hennig." The book is composed of contributions from a Linnean Society symposium that celebrated Willi Hennig's 100th birthday, and it was the organizers' intent to mark his legacy with a book that both looked back at Hennig's historical impact on phylogenetics, and tried to assess how his contributions are still relevant today. All the plesion discussion above is a distraction that has nothing to do with either our book or with Baum's review.

Does the future of evolutionary biology rely on the contributions of one 19th Century English biologist? Does the future of physics rely on the contributions of a 17th-Century English physicist/astronomer? Probably not. But that does not mean that we do not honor the contributions of Darwin or Newton or deny that subsequent work "rests on their legacies." As Newton himself said, "if I see further, it is because I stand on the shoulders of giants."

The fact that people are still arguing about whether or not classifications ought to be based on monophyletic (in the Hennigian sense) groups is a pretty clear indication that Hennig's ideas remain pertinent in the 21st Century.

The Legacy of Willi Hennig is, unfortunately, ambiguous: as somewhat exaggerated - but in principle true - summary Samuel Johnson's words (of course concerning another question) can be quoted: his views are – “both new and good, but what’s new [cladistic classification – RBH] is not good and what’s good [cladistic principles in phylogeny – RBH] is not new”. Unfortunately, Hennig's dogmas have been considered by some "decision makers" (funding distributors, editors of "high-ranked" journals &c.) as "divine revelation" to be obligatorily accepted and followed by anybody, and in this sense his "legacy" can, indeed, determine the future of systematics... As I wrote (Hołyński 2010: Is paraphyly indication of poor taxonomy? – open letter to Drs. Carvalho and Ebach) "its impact on taxonomy has been truly revolutionary – and, as such (revolutions are generally much more efficient in destruction than in building the promised “better”), disastrous".

It would be great to have both titles in open access to allow the scientific community evaluate both of them - the book and the review

This discussion about paraphyletic taxa is out of date, since the concept of plesiomorphon have been introduced.

In English see:

http://www.insecta.bio.spbu.ru/z/syst_I_2.htm#Plesiomorphons

http://www.insecta.bio.spbu.ru/z/plesiomorphon.htm

Sorry, but it can be said with equal (or greater...) right that the "concept of plesiomorphon" is out of date since the concept of taxon has been (much earlier!) introduced! The "concept of plesiomorphon" is just an element of "discussion about paraphyletic taxa" - no more!

I'm not going to say anything about paraphyly, except maybe, what's old is new again. If anybody would like to read my chapter in the above book, "Are we all cladists?", which bears the brunt of David Baum's critique, I would be glad to send you a private copy.

cheers,

AB

Hi Andrew, I would like to take your offer and receive a PDF of your chapter. You could either send it via RG or email [ ee.gutierrez.bio @ gmail.com ] Thank you! Cheers, Eliécer

Me too, please send to [email protected] Thank you Andrew, all the best in 2018!

To Roman Bohdan Hołyński:

If somebody does not know insects, for him any insect is only an insect;

If somebody knows insects, he distinguishes many kinds of them;

If somebody does not know taxonomy, for him any taxon is only a taxon;

If somebody knows taxonomy, he distinguishes various kinds of taxa, such as holophyletic, plesiomorphons, paraphyletic, polyphyletic.

I did not read the story about One Mid-20th-Century German Entomologist, because I know one more person with the same opinion, One Mid-19th-Century English Carcinologist, so they should be discussed together.

Hi Nikita! I would like to answer, but unfortunately I do not really understand what do you really wish to say? The contentious question in "the discussion about paraphyletic taxa" is not whether "plesiomorphons" (groups of which we cannot reliably say whether they are holophyletic or paraphyletic) do exist or not (of course they do!), but whether paraphyletic groups are or are not "full rights" taxa (i.e. whether classification should be based rigidly on branching pattern of the hypothesized genealogical tree with disregard of all observable facts, or on all available evidence). According to Hennig paraphyletic groups are invalid, (i.e. are not, in fact, taxa); in e.g. my (and many others) opinion, to the contrary, avoidance of paraphyly leads frequently to artificial groupings (i.e. to pseudotaxa).

I interpreted your earlier comment as the voice on Hennig's side (only holophyletic groups are true taxa), but now you list "holophyletic, plesiomorphons, paraphyletic, polyphyletic" among "various kinds of taxa" apparently in full accord with my view! Which of these two interpretations is correct?

Anyway, I do not understand how the introduction of the concept of plesiomorphon could resolve the discussion of the validity of taxa known (or believed to be known) as paraphyletic...

All the best! Roman

PS. By the way, who was that Mid-19th-Century English Carcinologist (my Wife is carcinologist, so this might be interesting to her)?

It seems to me that any legislation of any personal (personified) legacy is just a reproduction of once very famous (among Soviets) Lenin’s declaration “The teaching of Marx is all-mighty as it is the right one”. Devoted Hennigians use to proclaim the same about “the teaching of Hennig”. To me, such a standpoint fundamentally contradicts evolutionary epistemic view of development of any scientific discipline, with this view being expressed, best and shortest, by Ecclesiastes’ wisdom (to which George Harrsion added his penny) “all thing must passed away”. And I don’t thing that the term-games with any kind of “...ons” (taxon, phylon, parataxon, metataxon, pseudotaxon, plesiotaxon... etc) will secure this “teaching” from exhausting its creative potentialities some time.

The question posed by David Baum in the title of his book review, "Does the future of systematics really rest on the legacy of one mid-20th-Century German entomologist?" is deliberate distortion of our book's title, :The future of phylogenetic systematics: the legacy of Willi Hennig." The book is composed of contributions from a Linnean Society symposium that celebrated Willi Hennig's 100th birthday, and it was the organizers' intent to mark his legacy with a book that both looked back at Hennig's historical impact on phylogenetics, and tried to assess how his contributions are still relevant today. All the plesion discussion above is a distraction that has nothing to do with either our book or with Baum's review.

Does the future of evolutionary biology rely on the contributions of one 19th Century English biologist? Does the future of physics rely on the contributions of a 17th-Century English physicist/astronomer? Probably not. But that does not mean that we do not honor the contributions of Darwin or Newton or deny that subsequent work "rests on their legacies." As Newton himself said, "if I see further, it is because I stand on the shoulders of giants."

The fact that people are still arguing about whether or not classifications ought to be based on monophyletic (in the Hennigian sense) groups is a pretty clear indication that Hennig's ideas remain pertinent in the 21st Century.

Thank you for your comment, Andrew. I agree that the discussion might have deviated from what is actually on the book and the corresponding review/opinion piece. Hence, to help keeping discussion on focus, I will copy/paste below as much as the text in the review as I possibly can. Hoping that participants of this thread can share their views and we could all enjoy a healthy discussion/debate (either writing or merely readying participant comments).

------

part 1/6

"DOES THE FUTURE OF SYSTEMATICS REALLY REST

ON THE LEGACY OF ONE MID-20TH-CENTURY

GERMAN ENTOMOLOGIST?

[By] David A. Baum

Edited by David Williams, Michael Schmitt, and

QuentinWheeler. Cambridge and New York: Cambridge

University Press."...

"The Systematics Association’s edited volume, The Future of Phylogenetic Systematics: The Legacy of Willi Hennig, has an intended audience of systematists from the cladistics school. This is signaled both by the subtitle referring to Willi Hennig, eponym of that community’s academic society, and a lineup of authors that includes almost all living luminaries in that field. But if those clues did not suffice, the content of many of the chapters would quickly convince casual readers that this is not a work of mainstream phylogenetics or evolutionary science, but rather comes from a perspective in which “evolutionary history” is viewed suspiciously or downright rejected. As a result, this is a book that only a self-identifying cladist could embrace, but one that someone with a fascination (morbid or otherwise) for the cladistic mindset might enjoy thumbing through. It is from the latter, somewhat voyeuristic, perspective that I write this review. " [see part 2/6, below]

continuation. part 2/6

The first thing to explain about this volume is its self-contradictory title. How could a publication on the “future of systematics” be almost entirely about its history? This is not fully explained by the editors when they say that: “The primary aim of this book is to act as a beacon to the future, as well as a light on the past” (p. 6). Although shedding light on the past is easy enough to understand, what does it mean to be a “beacon to the future”? A cynical view is that their goal was to rewrite history so as to situate the cladistic school as the only true followers of the prophet

Hennig. Indeed, this is suggested in Platnick’s foreword when he expresses the concern that “the farther systematists depart from Hennig’s clear vision, the harder it will be to obtain the actual tree of life” (p. xv), with the implication that a correct look at the past will help avoid an unfortunate slippage into heterodoxy. However, even if the editors’ agenda was shaped by the principle that, as Orwell put it in 1984, “he who controls the past controls the future,” there is nowhere nearly enough cohesion among the 19 chapters to achieve this goal. Rather, the book feels more like a group of elders recounting their exploits and those of their ancestors, interspersedwith nota- littlemoralizing about the sad state of today’s youth.

The first four chapters chronicle Hennig’s life and present some anecdotes to describe reactions to his perspectives in different parts of the academic world. This provides an opportunity for readers not previously familiar with Hennig to pick up the basic story. He was an insect taxonomist who played an important role in defining the primary agenda of systematics as discovering and naming groups of organisms that are more closely related to one another than to anything outside the group. Hennig, like the botanist Walter Zimmermann, interpreted relatedness strictly in terms of recency of common ancestry and argued, therefore, that only monophyletic groups are valid taxa. Most importantly, Hennig proposed a general strategy for identifying shared derived traits as evidence of monophyly. As a result, the English translation of his book Phylogenetic Systematics in 1966 was a watershed event in the history of systematics. It ignited broad debate about the field’s goals and led to the eventual development of formal methods for phylogeny reconstruction, including parsimony (as stressed in the book) but also (more commonly used in the broader field of systematics) statistical methods based on maximum likelihood and Bayesian inference.Hennig’s role in triggering the conversion of systematics from a narrow discipline studied only by experts on particular taxonomic groups to a mainstay of evolutionary biology, epidemiology, and even ecology justifies some retrospection and historical analysis."

[see part 3/6, below]

continuation. part 3/6

Unfortunately, as a historical treatise, the volume falls short. Many chapters summarize perspectives on various debates that emerged among the scientists who claimed to have adopted some or all of Hennig’s views. As might be expected given that the authors are not professional historians, these contributions generally tell us more about the authors’ current agendas than about the actual record. In that background Rainer Willmann’s chapter, The Evolution of Willi Hennig’s Phylogenetic Considerations, stands out both as the longest in the book (72 pages) and the one that rests most solidly upon careful and critical analysis of Hennig’s writings.Willmannseems genuinely concerned with understanding what Hennig actually thought rather than using Hennig to justify particular perspectives or approaches. Although he does a good job of showing how Hennig defeated the self-named evolutionary taxonomists and their champion ErnstMayr, it seems tome that he presents an overly flattering picture of Hennig, conveniently downplaying areas where Hennig was muddled or self-contradictory.

Notwithstanding the snooze factor of the book as a whole, there are a few new perspectives to be gained. Minaka reviews the history of methods for studying the genealogy of manuscripts and languages, and also provides an amusingly complex, pictorial summary of the history of systematics since 1930. Likewise, Bruce takes an intriguing look at the contrast between preformationist and epigenetic views of development and ties these to the nature of species as either taxa or creative players in evolution. And Mooi and Gill explore the relationship between Hennig’s auxiliary principle (the idea that the existence of an apparent synapomorphy provides prima facie evidence of a clade) and his notion of reciprocal illumination (the idea that trees reconstructed from many characters can be used to reevaluate character delimitation). However, all three of these chapters, and many others, are too deep in the weeds for any but a committed insider to really digest. This tendency to long-windedness is confounded by a lack of chapter abstracts, making it even harder for readers to figure out what each author is really trying to say.

If there is one chapter to read you might want to look at Brower’s Are We All Cladists?, since this provides the clearest picture of the cladistic worldview. It is true that Brower has made many of these points before, but if you do pick up the book, a close analysis of his chapter is probably the best use of your time. For this reason, I will spend most of the rest of this review exploring Brower’s perspective and contrasting it with the phylogenetic school of systematics."

[see part 4/6, below]

continuation. part 4/6

"As Brower clearly explains, the objective in phylogenetic systematics is to obtain an inference that is as close as possible to some external truth (actual evolutionary history), whereas in cladistics, as he defines it, there is no notion of truth beyond the maximization of agreement among characters. This distinction between, respectively, the correspondence and coherence notions of truth is captured vividly by Brower’s metaphor of a pair of archers: a phylogenetic archer shoots arrows in the hope of hitting a hard-to-see bull’s-eye (Brower would say an invisible bull’s-eye), while a cladist shoots many arrows in the same direction, and then defines the place that they are clustered as the bull’s-eye.

You might be asking, why would a scientist want to obtain a tree unless they believed it resembles something that exists in the world? Brower’s answer seems to be that this is the best we can do. In order to assert that a tree actually existswewould have to knowsomething about howcharacters evolve, but the only way to know that would be to have prior knowledge of phylogenetic histories that actually transpired. Thus, he seesmainstreamsystematics as trapped in a tautology: to infer a tree we need to know howcharacters evolve; to infer how characters evolve we need a tree. Thus, all a good scientist can do is to analyze the characters in themost neutralway possible and accept the resulting cladogram as the true relationships (or at least “best”) of the organisms scored. I will argue below that Brower is wrong because he underplays the principle

of reciprocal illumination, but let us first follow

his lead and talk about Hennig.

In keeping with the theme of the volume, Brower’s first move is to try and show thatHennig’s views were closer to cladistics than to phylogenetic systematics. The author kindly warns that “the reader should consider arguments presented here with a degree of circumspection: who knows what Henning would have thought of computer-generated phylogenetic trees . . . ?” (p. 92). I appreciated that caveat, since I arrive at the opposite conclusion, namely that Hennig subscribed to a correspondence notion of truth. In his book Hennig (1966) can be seen to frame the challenge along the lines: we know that new lineages form when they split into descendant lineages (see Hennig’s Figure 4), and we can reason that the descendants of an ancestral lineage inherit the characters that were present in the ancestral lineage, so we should be able to identify monophyletic taxa by identifying shared derived characters (synapomorphies). In other words, he had a clear sense of an underlying process and used that as a guide for developing his methodology. To be sure, his methodology is not structured as a statistical inference challenge. It took the genius of Joseph Felsenstein to make that connection in the late 1970s and early 1980s. Nonetheless, we can be pretty sure that Hennig developed his methodology with the goal of learning something about the world as it actually is.

Although I would stand by my conclusion, we can forgive Brower for seeing things otherwise. Hennig’s writings are confusing and probably also confused. In my opinion, Hennig never quite resolved the (apparent) conflict between empirical taxonomy and conceived reality. So it is anybody’s guess whether he would have resonated more with the cladistic approach (empirical taxonomy is all there is) or the phylogenetic one (we aim for taxonomy to reflect reality, but know we will never quite get there).

Brower’s chapter then reprises well-trodden cladistic arguments against viewing trees as estimates of true evolutionary history. His core idea is that the distribution of characters serves as the key evidence that evolution happened, so it is unscientific to use assumptions about the evolutionary process to help us turn character data into an estimate of evolutionary history. Since we should not use any ideas as to how characters evolved to build a tree, all we can do is report the tree that is most consistent with all of the characters we have scored. That is to say we should use parsimony as our sole criterion. However, in making this argument Brower forgets one of Hennig’s most important contributions, the principle of reciprocal illumination."

[see part 5/6, below]

continuation. part 5/6

"When systematists began inferring trees, mainly by parsimony, they noticed certain patterns in the evolution of molecular data. For example, transitions (adenine-guanine or cytosine-thymine conversions) almost always occur at higher inferred rate than transversions (the other four base substitutions) and, likewise, third codon positions change more frequently than first or second codon positions. Since each of these patterns can be readily explained by evolutionary models—the former based on unequal mutations rates, the latter based on purifying selection against amino acid changes—it makes sense to develop model-based methods of phylogenetic inference that can take account of the inequality of rates of evolution across characters (and across lineages). This is really just a case of reciprocal illumination. We convert character data into trees (perhaps using parsimony) and then use the resulting trees to update our understanding of evolution, resulting in the development of more accurate methods of phylogenetic inference. This is not circular because the to-and-fro is not just within one group of organisms and one set of data. Rather, we use multiple data sets from across the tree of life to help us bootstrap our way to a clearer understanding both of phylogenetic history and character evolution.

In contrast to the phylogenetic approach, cladistics, as presented by Brower, lacks scientific ambition. Since evolutionary history is viewed as unknowable, all we can do is observe characters and summarize their consistent patterns. This is a surprising position since, as Brower admits, even characters are not knownwith certainty: we need to make all kinds of assumptions about the real world to score characters. For example, when we convert electropherograms or the flashes of light or charge detected by a nextgeneration sequencer into a linear sequence of A, C, G, and T we are making very firm assumptions about how the world works. But cladists routinely accept these molecular and biochemical assumptions when they convert the raw data into a character matrix. Why are molecular biological models allowed but evolutionary models are not? Likewise, justifying outgroup-rooted, flat-weighted parsimony based on the intuition that it best summarizes character agreement seems indefensible when there are multiple methods that can equally claim to do the same (e.g., implied weighting, three-taxon statements, or compatibility analysis). Furthermore, it seems misguided to justify the use of parsimony on such philosophical grounds when the ultimate job of science is to use empirical data to enhance our understanding of the natural world. In short, I cannot help but view cladistics, at least as defined by Brower, as a sad retreat from the practice of science.

The last section of Brower’s chapter provides an interesting comparison to the last chapter of the book: Quentin Wheeler’s This Struggle for Survival: Systematic Biology and Institutional Leadership. Both take a look at the reality that cladistics is becoming a more and more marginal field, with only one major bastion left (the American Museum of Natural History) and a handful of adherents across the United States, Latin America, and Europe. Wheeler focuses on the loss of taxon specialists, a reduction in knowledge of morphology, and his fear that systematics is being relegated to just creating trees for other scientists to use. Although I share his concern about the loss of biodiversity and the urgent need to increase knowledge of natural world, I do not share Wheeler’s pessimism about systematics as a field. In the modern era former disciplinary barriers are eroding meaning that systematists are now empowered to be those “other scientists.” As systematists we can both infer trees and then use them to better understand diverse evolutionary phenomena. So, although I do not deny that it would be great if there were new and expanded investment in museums and herbaria and scientists studying biological diversity, systematic science itself seems to me to be in pretty good shape."

[see part 6/6, below]

continuation. part 6/6.

"If Wheeler focuses on the heart of systematics, Brower focuses on its soul. He is appalled by what he sees as the technophilia of mainstream systematists and their flawed conceptions: “whatever ‘philosophy’ they may hold, if they have any at all, is antithetical to ours” (p. 108). But, if its virtues are so clear, why has cladistics lost so much ground to phylogenetic systematists? The problem, Brower suggests is cladists’ penchant for in-fighting and getting hung up on “excommunicating our fellows for relatively insignificant heresies” (some of which are on show elsewhere in the volume) when, instead, they should be “devoted to proselytizing to unbelievers” (p. 109). He ends with the plea to his fellow cladists to “work together to present a united front against these assaults on reason” (p. 109).

If this sounds a weirdly evangelical to you, I would agree. I would contend that the failure of cladistics to grow is not because its proponents have been bad proselytizers, in fact they have proven effective at fostering cult-like adherence in some circles. Little could make this worldview clearer than a volume that says nothing about evolution and how we can study it and a lot about the writings of one historical figure (the prophet, so to speak) and a plea to hold fast to the movement’s orthodoxy. Rather, I think that cladistics has declined for the simple reason that the school has boxed itself into a fundamentalist ideology that is pretty hard to defend as science. This book, for all its attempts to reshape the future by revisiting the past, is unlikely to turn this tide."

Eliécer E. Gutiérrez and Andrew V Z Brower: thank you for providing us with a detailed, comparative and highly informative summation on the ’status quo’ of the ‘cladistics’ as it relates to ‘phylogenetic systematics’. This is an excellent baseline from which ‘the future of phylogenetic systematics’ can and I believe, eventually will emerge!

I am looking forward to the ‘the new synthesis’ which will recapitulate the contributions of: Linnaeus, Rafinesque, Weismann, Darwin, Hennig, Mayr and many others, including molecular techniques ....... leading to a foundation of genomic [DNA based + allocation of adaptive traits], phylogenetic systematics based on a ‘total evidence approach,’ i.e. integrative taxonomy. The revival already began here!!

As an example, I am attaching a figure (Fig. 1.) illustrating the type-species of the genus-group taxa of Anglewing butterflies, with available names. A monophyletic clade (sensu Hennig, 1976).

The ~35 species of Anglewing butterflies, aka Tortoiseshells or Commas represent a monophyletic clade [sensu Hennig, (1967)]. The monophyly of the clade is explicitly and unequivocally indicated by the synapomorphic, shared, highly derived trait ‒ the cryptic ventral wing phenotype. The resting, mating, diapausing butterflies with their wings closed, blend-in with the surroudings [concealment camouflage]. The monophyly was recovered by a total evidence, including molecular data, Nylin et al (2001). Fig. 1 shows the type-species of the seven avaialable genus-group names: Nymphalis Kluk, 1870; Aglais Dalman, 1816; Polygonia Hübner [1819]; Inachis Hübner, [1819]; Euvanessa Scudder, 1889; Kaniska Moore, 1899 and Roddia Korshunov, 1995. The oldest available genus-group name: Nymphalis Kluk, [1780] has a publication priority over the other available names, should these taxa be deemed as congeneric with Nymphalis (ICZN Code, Preamble, Principle of Priority). Every genus-group name is permanently linked to its type-species (ICZN Code, Principle of Typification). The type-species is like a name bearing anchor, linking the genus-group name to a single species-group taxon. The ICZN Code refrains from making any taxonomic judgements.

I am investigating whether Nymphalis clade (sensu lato) is phyletically one singular taxon, or if there is any evidence suggesting that the clade consists of multiple, automomous [segregated] phyletic lineages. Wahlberg et al (2005, 2009) synonymized Inachis with Aglais; Roddia with Nymphalis and Kaniska with Polygonia. Kaniska was again recognized as a distinct, separate genus (Wahlberg (2003).

Fig.1. Anglewing butterflies: type-species - copyright 2017, Norbert G. Kondla

References provided on request

With all due respect, Joe Belicek, it seems that you are hijacking this thread. I hope you find the help you are looking for, but I really hope further comments here will focus on discussing the ideas stated in that book review and book.

As you wish. Good luck. I am gone from ‘your’ turf. In my opinion, the ideas in the book per see are already well known and assimilated into the mainstream of evolutionary systematics. Adios.

I find the terminology in the review weird. It wouldn't occur to me to restrict "cladistics" to pattern cladistics, or to implicitly equate pattern cladistics with any use of parsimony. I have used parsimony to approach (probably with limited success) the true phylogeny, so I'm not a "cladist" but a "phylogenetic systematist" in Baum's terminology; I've used parsimony because (as discussed in the preprint I just uploaded) it seems to be at least as good as Bayesian inference and better than likelihood with the particular kind of dataset I have to deal with, not because of philosophical considerations; and I don't call myself a "systematist" but a phylogeneticist, because I don't classify – I test phylogenetic hypotheses, and I name clades, without a "system" anywhere to be seen.

An argument has been made elsewhere that Hennig's actual method was not parsimony or for that matter compatibility, but something unique. Specifically, he thought that if you have any homoplasy in your dataset, that means you've made a mistake somewhere, and you need to reevaluate the entire dataset: in other words, complete convergence does not exist, it can only seem to exist if you don't look closely enough. This is obviously wrong, especially but by no means only for molecular datasets. Thus, nobody – not even the pattern cladists – uses Hennig's exact method today.

yes it does. Even if you do not accept cladistics. The value of Hennig's legacy is his ideology and (funny but true!) the set of verry useful terms.

It's not easy to neglect that a lot about taxonomy is actually about the terminology.

Interested people may look at this English paper

Luzzatto M, Palestrini C, Passerin D'entrèves P (2000) Hologenesis: The last and lost theory of evolutionary change. It J Zool 67:129–138.

It deals with a theory of evolutionary changes that anticipated Henning by several decades, made by Daniele Rosa then at Turin University

...Hennig didn't propose a theory of evolutionary changes...?

David: no, Hennig only formulated some (not really new) rules for reconstruction of genealogical relationships (phylogenetic branching pattern), introduced some sophisticated (some of them really useful) terms, and suggested (unfortunately with much success...) new confusing meanings for some well known old ones...

That's how I had understood it, thanks.

There is an intriguing aspect to Gippoliti Spartaco's comment about Rosa's 'anticipation' of Hennig. In the 1960's Leon Croizat pointed out that there were such close similarities in presentation of not only the concepts but also some diagrams that he suggested this might be a case of plagiarism. There is no way to prove this accusation either way, although Hennig was apparently in Italy during the latter part of WWII so it is conceivable that he did come across Rosa's work. This will probably remain forever an unanswered question.

Perhaps Olivier Rieppel or Michael Schmitt, who have both worked extensively on the roots of Hennig's ideas, might be able to shed some light on this question.

Someone on Wikipedia claims that during his time as prisoner of war in Italy Hennig began to draft his systematics work. Intriguing as to why that took place at that time and place.Could be pure coincidence. I doubt that Rippel or Schmidt could shed any more light on the question as there is no actual paper trail. It would require a copy of Rosa with dated annotation by Hennig to give any direct credence.

In Michael Schmitt's Hennig biography, (Schmitt, M. 2013. From taxonomy to phylogenetics - the life and work of Willi Hennig. Brill, Leiden.), he devotes a box on pp. 121-122 to the question "Did Hennig steal from Daniele Rosa?" His conclusion is, probably not. Schmitt also notes that Hennig cited a German translation of Rosa's 1899 book in regard to ideas about character polarity. So, even if he was familiar with and adopted elements of Rosa's work, he cited his source. What else can one do?

"Everybody's go to have someone to look down on" Really easy but short sighted to denounce some dead and gone genius as flawed with the flimsy explanation that it is not modern. There is far more logical thinking in Hennig's writings than in most points made here. Oh and I am not even a strict cladism but monophyly and synapomorphy seems inarguably valuable concepts for a cladist (not me) and a phylogeneticist (I am one).

Its really not possible to assess the significance of Schmitt's conclusion of 'probably not' without knowing why.

Patrice, please explain what you mean by 'flimsy explanation that it is not modern.' and what difference are you making between a 'cladist' and a 'phylogeneticist'? That would help me understand the points you wish to make.

John Grehan

I should say that I am not a strict cladist, It seems to often to require a very cumbersome set of empty taxa to balance other clades that have taxa. But perhaps I misunderstand strict cladists.

My methods for inferring evolutionary history include phylogenetic analysis (primarily maximum likelihood with a smattering of Baysian and a good dose of parsimony where appropriate). But my interpretation of the relationships definitely depend on Hennig's excellent criterion of monophyly and synapomorphy, Synapomorphy is by definition, similarity by descent so it alone defines monopoly (natural groups). Paraphyly and polyphyly define groups whose membership are more closely related to members outside of the clade.

The remark about "flimsy explanation" refers primarily to remarks like Nikitas insistence that paraphyly discussions are outdated and various other criticisms of Hennig.

Patrice: if you accept the Hennigian dogma rejecting paraphyletic taxa, then you are a cladist: rejection vs. acceptation of paraphyly is just the primary difference between the cladistic and synthetic ("evolutionary") "taxonomical philosophy"! And it is not a difference in phylogenetic methodology but only in taxonomic conclusions: I do accept paraphyletic taxa (in fact, I consider their rejection completely illogical and, in fact, unscientific!), cladists do not, but our phylogenetical reconstructions would be identical - only our classifications would (often drastically) differ!

"Cladistics"/"cladism"/"cladist" has been used in several quite different meanings. The following list may not be exhaustive:

– the taxonomic position that only clades should be accepted as named taxa;

– phylogenetics as a science (as opposed to the art it used to be);

– the position that phenetics-based methods (UPGMA, neighbor-joining and the like) should not be used in phylogenetics;

– the position that only so-called "maximum parsimony" should be used in phylogenetics (as opposed to parametric, model-based methods – maximum likelihood or Bayesian inference).

Hennig happens to have championed the taxonomic position that only clades = monophyla should be named taxa and to have published the first reproducible method for phylogenetics (...though it was neither maximum parsimony nor for that matter maximum compatibility as some have thought, and it's really unworkable and makes the flatly unrealistic assumption that full convergence never happens). These are two separate things that have nothing special in common.

Full disclosure: my own positions on these issues are:

1) Phylogenetic nomenclature, an idea that really goes back to Goodrich's (1916) detailed presentation of Amniota, Sauropsida and his new name Theropsida as a node-branch triplet.

2) Every method of phylogenetics works when its assumptions are met. For a detailed discussion see the relevant section in the Discussion in my 2018 preprint.

I can't understand why so many systematists still struggle to understand the distinction between a phylogeny and a classification. Cladistics and cladism are often used as synonyms although some people are cladists (i.e. they reject all non-holophyletic groups) without doing cladistic analyses (using ML or BI instead) while others are doing cladistic analyses but accept paraphyletic groups as natural. My guess is that there has been too much (cladist) propaganda in the use of systematics' terminology. In practice, even in phylogenetic reconstruction, synapomorphies aren't as important as they were since computer programs build UNrooted trees, and only thereafter root them. Homologies, not synapomorphies, are important today.

Whether a ML or BI analysis counts as "cladistic" depends on who you ask. Me, I don't think the question is interesting...

Phylogenetic nomenclature is the position that we don't need classifications at all. We just need the tree and labels that we tie to it in carefully defined places.

Interesting comment by Damien that " In practice, even in phylogenetic reconstruction, synapomorphies aren't as important as they were since computer programs build UNrooted trees, and only thereafter root them. Homologies, not synapomorphies, are important today."

My impression is that using tree building techniques to create phylogenies and therefore identify the homologies as a result of the tree is cladistically problematic. Mostly the tree building technique is done with molecular data for which the prior identification of synapomorphies is problematic since bases may swap out back and forth and even more problematic is that with alignment, which is a purely phenetic best fit exercise, create homologies (matches) that do not actually exist in nature. But for one reason or another most biologists view the molecular data as sufficiently reliable to accept, whether or not it is strictly cladistic. The added problematic layer comes with the metaphysical assertion that molecular trees are falsifiers of any contradictory morphological tree constructed from cladistic methods (prior limitation to analyzing apomorphies). Some try to get around this by combining the 'total evidence' but this is like mixing apples and oranges. Most of the time there is little controversy, but there are some major anomalies such as with hominid systematics where cladistic morphology supports a human-orangutan clade while molecular data support a human-chimp clade.