A manuscript for the journal Asklepios.
Is classification science or art? Part 1.
The common reaction and assertion is that classification (of plants) is a matter of opinion. It is also often stated to be an art, and even the late Prof.A. Cronquist in writing a book on the principles of plant taxonomy, describes it as ‘artful science’. John Lavranos in a letter (1998), and an anonymous referee for SA Journal of Botany in an assessment of a manuscript, state that taxonomy is to a degree ‘art’. It is necessary to examine this belief because it is intrinsic to our understanding of plants, the names we use for them and how we communicate about them.
Firstly I have to ask myself if I am qualified to undertake this examination, and if I have the credibility to do so. I have a Master’s Degree in Science, and experience in research, education and advisory work. I am an honorary member of the Aloe and Succulent Society of South Africa, an honorary member of the Haworthia Society, and a Fellow of the Cactus and Succulent Society of America. I have been involved in the classification of things for as long as I can remember, and have been party to the classification of the genus Haworthia (Asphodelaceae). I have also been attendant and attentive to the controversy and conflict associated therewith. This disputation in Haworthia dates back from the time of Uitewaal, Resende and G G Smith in the late 1940s, and despite a mountain of literature nothing has changed. I am also aware of similar disputes that rage and have raged elsewhere, and they simmer in Asklepios. Therefore I have naturally inclined to seek an explanation for such controversy, and hence a solution for, avoidance of or deliverance from, such conflict. If the perception is true that classification is an art, it means that the whole edifice of biology, since all of biology is built on the classification into species, is built on a foundation of art.
My own experience in Haworthia has suggested that the level of cognition in the process of making and assessing of classifications, is remarkable for its absence or its mediocrity. It is immediately obvious that cognition is also missing in the question “art or science”. It is absolutely a wrong question.
The fact is that classification is a fundamental activity of consciousness and probably so at all levels. Any living organism has to make the distinction (the classification) between what will lead to survival and what will lead to death. As consciousness proceeds to higher levels so does the complexity of the classification. As humans we are presumed to have the highest complexity and can even classify our activities into science or art. We pursue truth and knowledge, and we pursue pleasure, diversion and entertainment. We apply methodology, logic and reason to the pursuit of knowledge and we call this science. We apply imagination, fantasy, emotion, imagery and creativeness to expression of our individuality and we call this art. All these aspects of mental activity can be present together in either activity of science or art, and we classify the product of this activity even if this is only into “good” or “bad”.
The fundamental question in respect of the evaluation of a result of the activity of science is.. “Is the product true?”. In respect of art..”Is the product evocative?”. Therefore it is not a question of classification being “art or science”. It is only a question.. “Does the classification meet the needs of science. Is it true?” The question can be elaborated also to ask..
“Does it present a significant understanding of the subject?”
“Does it withstand proper intellectual scrutiny?”
“Does it meet the needs of the community it serves?”
If the answers to these questions are in the negative, then perhaps we can dismiss a classification as “bad” and even call it art if we so like.
The problem thus is that classifications often do not withstand these questions. It could be a consequence of the fact that the process is practised and treated as art. A point then overlooked is that, if classification is practised as art, then surely taxonomists should be trained as artists and at least be qualified in some way to do the job?. One can, of course, argue about the meaning of the word art to denote “skill”. The extrapolation of observed facts to theory is perhaps a human creative skill. But that is not art, it is the essence of wisdom and good judgement and the theory is testable.
In my life’s experience, taxonomists in zoology and botany, have tended to focus on groups which are ‘available’. Hence, if someone was undertaking a revision of any specific group, it was a question of hands-off to anyone else. Wherever this dictum has been disregarded, controversy seems to have resulted. Taxonomists tend to be insular and there may be psychological and personality factors in their choice of occupation. Such psychological factors may influence their activities and judgements as either artists or scientists. Unfortunately both scientists and artists may require validation and recognition of their work and the point is that there are personal factors which need to be considered as well. These include the questions not only concerning the competence and “adaequatio” of the individual, but concerning motive and intent. These are factors which influence the quality of an individuals activities whether in science or art. To my knowledge nobody has confronted the aspect of “adaequatio” better than Schumacher (1980).
My own impression is formed from my life’s experience. This is that plant classification has not advanced conceptually since amateurs and professional alike befuddled the perceptions of Charles Darwin. They did this by discarding the idea that there were God-created ‘species’, which is something I do not think Darwin did. He is credited with the conception and description of evolution and the origin of species. He did not necessarily conclude or prove that evolution (and the existence of species at all) were products of chance. Even Einstein’s famous quote “I do not believe that God plays dice” does not prove anything, other than that perhaps he was an even greater scientist than we give him credit for. The fact is that whatever Darwin may have thought, ‘species’ came to fall into the intellectual domain and were whatever man ordained them to be. Classification thus can be impressionism under the guise of science. Early taxonomists were actually little better than descriptive writers (like stamp collectors), and many of us still tread the same mill. Persons like Masson, Haworth, Salm-Dyck and the likes, with the limited material available to them, had virtually no basis whatsoever for recognising species. The only classifications they could produce was for the limited material they had to hand.
Schumacher’s book should be compulsory reading for all would-be artists and scientists. The book demonstrates to me that society needs to ask itself what ‘science’ is. Modern science seems indeed to be only a process of acquiring knowledge and understanding of inanimate matter. Following Schumacher, classification is a ‘divergent problem’ and such problems are not solvable by the conventional mechanistic, reductionist, Cartesian approach that appears to work for ‘convergent’ problems (for which there is apparently a single correct solution). Science is not the aseptic objective scene (‘not subject to argument’ .. Lavranos, 1998) we think it to be. In my personal experience I have witnessed the sequential grabbing and clutching at cytology, scanning-electron microscopy, chromatography, electrophoresis, molecular biology and now DNA, as technological breakthroughs which will solve biological problems in a reductionist manner. My conclusion is that they have done as much to complicate issues as they have to explain them. Schumacher speaks about the “dethronement of the DNA-mythology of molecules becoming information systems”. The reductionist approach is that of believing the smaller we see, the more we understand. At least in the case of physics it appears to be the case that the smaller we see, the more there is to understand (Capra, 1982). This may be true of biology as well.
I think a reason why so many classifications fail is because we may have an outdated view of species (forget for the moment the general absence of even a definition), and even a wrong notion of how genetics actually works. It was interesting to find a report on the cybernet by Dr Mae-Wan Ho of the Open University, U.K. He/she describes the paradigms of the new and the old genetics. It lightens my heart considerably to find support for my conviction that much intellectual methodology (like cladistics) is itself subject to review and possibly even obsolescence. Sometimes it may be waffle obfuscated by “a language which does nothing but strain goodwill”. Capra went so far as to quote an author who said that biology would come to need a new language in the impending new paradigm of science. This ‘new genetics’ must surely strain the way we see ‘characters’ and attach weight to them.
Mae-Wan Ho states:-
1.Old genetics – genes determine characters in a linear, uni-directional and additive way.
New – genes function in a complex and non-linear network – the action of each gene ultimately linked with that of every other, causation is circular and multidimensional. (‘reticulate’ might be a better word than ‘circular’, it is still non-linear.. author).
2.Old – genes and genomes are stable and except for rare random mutations are passed on unchanged to the next generation.
New – Genes and genomes are dynamic and fluid, they can change in the course of development, and are subject to feedback metabolic regulation.
3.Old – genes and genomes cannot change in response to environment.
New – genes and genomes can.
4.Old – genes are only passed on in a breeding process.
New – genes can be transferred between non-breeding individuals and un-related species. (This is even hard for me to swallow. I have understood it claimed that hereditary material may be non-chromosomal. It is not unimaginable that mechanical transfers can occur).
What I find disconcerting is the lack of any indication among many….
1.taxonomists, that they are really aware of what it is that they are classifying and identifying by the use of latin binomials.
2.botanists, that they know what taxonomists are doing.
3.botanists, that physicists may be looking at science differently, and why this is so.
4.laymen, that they are aware of the very weak foundation and organisation of both their faith and scepticism.
Recently while trying to address these kinds of problems in my own sphere of interest (viz. Haworthia), I was stunned to hear from a highly experienced and respected plant taxonomist, that there was no definition for ‘species’. I have said ‘stunned’ when in fact this was a suspicion of mine when I wrote my first Haworthia Handbook in 1975. I also use the word ‘stunned’ because the man may also have meant there is no need for a definition. It is a widely debated subject, and ‘everyone’ knows what a species is anyway. I deliberately wrote a chapter entitled “The genus and species concept”, so that readers would know what I was trying to do in listing species of Haworthia. That chapter seems to have been overlooked by anyone else interested in Haworthia. I am forced into a siege mentality by the weak publications that still so commonly appear directed at the classification of them. My integrity and judgements are thrown into confusion by writers who simply have not read or understood what has been written. There seem to be taxonomists who do not get into the field enough, they do not propagate and grow the plants actively enough, and they do not think widely enough. Commentators are often even less well qualified to express any opinion, and may also be caught up in the Cartesian and/or Newtonian belief system that there is a solid foundation on which a classification system can statically rest. Just give them time and technology and that foundation will be found.
My particular experience is possibly unique in that it involves many families, genera and species in both the animal and plant kingdoms. It is not that I am a great intellectual or academic. It is all too obvious to me that technical detail exposed by electron microscopy, cytological examination, chemical analysis and the like, do not result in unflawed results. John Lavranos is right when he says that these are also used subjectively. Classification is going to remain a source of frustration and conflict for as long as the paradigm of the 1940’s rules. This is the blind belief that problems remain unsolved simply because they have not been looked at closely enough. Capra considers the Cartesian reductionist paradigm to have failed us completely and that society generally has come to a turning point in the way we approach the problems of life.
In Haworthia there are few measurable characters. Those that are available are so indeterminate, nebulous or variable that large samples and complex formulae are probably required to recognise and circumscribe species. An intuitive approach is demanded. My confidence to use this approach has been based on experience gleaned from observation of other genera and also of other ‘researchers’. If I have any qualities that a scientist should have, I would like to claim that of ‘organised scepticism’. ‘Organised’ as opposed to a scepticism which is not even sceptical of itself. I produced a classification which was not a true revision, but one which was inferred from my general knowledge of biological systems. Other attempts have been made and are being made to treat Haworthia as a convergent problem. They have done and will do nothing but create confusion, stress and conflict.
A classification is supposed to be, and it should be, an hypothesis which can be questioned and tested in a logical and methodical i.e. scientific, way. There must be some reason and logic on which it stands, and reason and logic on which it falls. However, if there is no species definition, there is not even a beginning. As already mentioned, most of the early writers had no species concept whatsoever outside of some unexpressed notion that species were different kinds of things. Perhaps they also subliminally believed sexual compatibility was involved. In zoology this has not been a real problem because, in higher animals, at least, the principle that species are non-outbreeding groups of organisms holds fairly true. In plants it does not and naturally if the concept of the ‘species’ is not defined in some simple way, there can be little hope that classification will take place on any mutually agreed basis. How can it be a science, and how can any two people come to agreement? If the definitions are too complex their acceptance becomes “a matter of faith” and it is then no wonder that there is controversy and disagreement. The essence of science is method, repetition, and confirmation of observation. This is what taxonomists should be paying attention to.
I suggest that we need a species definition to be a postulate of biological science (rather than a vague concept that can be varied at will) and this is how I would word it:-
A species is a living dynamic system (“system” defined as per Collins Dictionary, 1982), composed of a group or groups of living organisms which are morphologically and genetically continuous in time and space.
The concept of a species therefore suggests a system of living organisms which have morphological and genetic variation. It occupies some describable niche in geographic space and it also has a past and a future. The physical basis for the recognition of a species is firstly its existence as a system in geographic space so that at least it can be found again. Second is the deposition of material in an herbarium and the pictorial and written public record that accompanies it, so that the observation and description can be verified. To the extent that it is subject to mensuration and statistical analysis, data should be so presented and so analyzed. The definition of ‘species’ does not suggest that the continuities are necessarily easy to identify or describe, nor that these continuities are static. It does mean that any classification hypothesis has to have a basic concept against which it can be tested.
Perhaps individuality creativity and subjectivity cannot be excluded from any scientific activity. If art is the cognitive expression of individuality it could influence theory but we should in fact use the word ‘impressionism’ for classification until such time as we are sure about what it is that taxonomists do. Thus if we now say that classification is impressionism AND a matter of opinion, we have to bring in the constraints that the writer Ellison put on opinion viz. everyone has a right to opinion, but it must be informed opinion. A scientific hypothesis is an informed considered opinion. We have the responsibility to educate ourselves. Everyone has a right to classify plants, but he has an obligation to be properly informed and properly qualified in terms of training, experience, and personal objectivity to express the ‘impressions’ he acquires. If these principles are applied, the audience will also be better able to form their own impressions which are more rational and reasonable.
My conclusion is that art and science are two quite different activities. Science is descriptive, explanatory and instructional, but above all it is re[eatable, testable and verifiable. Art cannot be substituted for science. Art is creative, emotive and expressive. Many of the ‘scientists’ in our midst may be good or bad artists, and they may be producing classifications which are artistic creations rather than science. The watch-dogs of science (the reviewers and the commentators) should be recognising and watching this. It appears to me that they may not even be aware of the nature of that which they are attempting to guard.
Although so different, both science and art should lead us to an understanding of what it really means to be human. Schumacher puts this very well for art.. “To treasure art simply for its beauty is to miss the point. The true function of art is ‘to so dispose the heart with desire of going up the mountain’ (of human understanding?)”. The true function of science is to pursue knowledge, but the disposition of the heart must be the desire for truth.
Is classification science or art? Part 2.
Nearly every commentator who has been constrained to express an opinion about the classification of Haworthia, has said that it is a ‘difficult’ group. In most cases it is doubtful if they are even qualified to comment. Now my experience and interest has not been remote and limited to Haworthia. I have expressed written opinions about Gasteria, Duvalia, Piaranthus, Aloe, Oxalis and some other genera. During my 18 years at the Karoo Botanic Garden I saw myself as entrusted with the task of knowing something of the (identification) classification and whereabouts of the plant species of arid Southern Africa. My conclusion today, after 40 years and more in the field where the plants are, is that all genera pose exactly the same problems. Prof. E.A. Schelpe used to joke that ‘taxonomy was easy if you did not have enough material’. Few (actually very very few) botanists really get out into the field and expose themselves to the diversity that is there. I have seen them pretend to do so, but in my opinion they do not even scratch the surface. In this second part of my article, I would like to examine and comment on classification as it pertains to the Asclepiadaceae and particularly the genera Duvalia and Piaranthus with which I have some familiarity.
John Lavranos (1998), maintains that Plowes has “an unequalled knowledge of the Stapeliae in the Herbarium, in cultivation, and above all else, in the field”. This is disputable in itself, but I do not think it has any relevance to his ‘splitting’ efforts. Perhaps Plowes has also not seen enough and it appears from his collecting records that most of his numbers are allocated to collections by other persons. Lavranos attributes to Reynolds the remark that ignorance leads to lumping and that ego and/or knowledge lead to splitting. This is an opinion which he is entitled to, but neither activity may necessarily constitute ‘science’. My opinion is that lumping and splitting both occur because workers do not have parameters within which to work and are given far too much latitude by an uncritical audience. Their competence and “adequatio” may not match their highest motives or intentions. I have worked and published with Plowes. With affection and respect, I have to question his classification. It does not satisfy my scepticism and I do not believe that his work in the asclepiads is rational. At one congress I had spoken of the artificiality of genera, and the erratic (chaotic) way in which characters occurred. Plowes agreed enthusiastically with me, yet nevertheless has proceeded with splitting Caralluma in direct antithesis of that consensus.
Dr Colin Walker’s (1997) comments on Plowes’ proposals for Caralluma should perhaps have been put some other way. Firstly Delanoy was wrong in stating “Plowes (1995) has demonstrated that the genus Caralluma .. “. He should have said ‘Plowes has suggested/proposed.. “. Secondly, Walker could have committed himself to a statement that Plowes’ taxonomy disturbs his perceptions of good classification. I certainly think there is a real problem. Thirdly, Walker could have emphasised that genera are even more subjective entities than species. Hence if the species are questionable (in the case of Caralluma Walker states there are 14 such species), the genera will definitely be so. Before we even consider genera, I think the problem lies in the absence of consensus about the reality of species. We can here consider Lavranos’ (1998) comment concerning the three Pachycymbium species. He says they display enviable uniformity. The truth is that if we apply the species definition I have proposed, it is fairly obvious that his three ‘species’ are in fact variants of but one. This can be easily demonstrated by going out into the field and looking at what is there in terms of a continuous system.
If I look further at the Asclepiadaceae, I can comment on Piaranthus and Duvalia which I used to help me understand Haworthia. These two genera are well researched (by U. Meve, 1994, 1997). They represented to me the easiest of the Asclepiad genera to work on particularly since they are geographically contained and occur in reasonable numbers as local populations. I was using these two genera to gain some insight into Stapelia and others. Frankly I am disappointed in the revisions by Meve. As J.K. Spearing (1998) commented.. “A careful analysis of Meve’s system (for Duvalia) reveals that in essentials it differs very little from Bayer’s..”. I also heartily endorse Spearing’s view that modern taxonomists are over-emphasizing details of morphological difference, and I think Meve has done just that. But Spearing continues by saying that they do this without adequate knowledge of genetical discontinuity. This last statement alarms me, because I consider that the modern taxonomist (in the case of Duvalia and Piaranthus, this is Meve) is also claiming support for his classification on the basis of cytological information. My alarm stems from Stephen Gould’s statement (paraphrased) – ‘When I see what is done with things that I do know something about, I am sceptical about what is done with things I have no knowledge or experience of’. Cytology, like SEM and other sophisticated ,technologically dependent characterisations, is not amenable to ordinary examination and scepticism. It is also part of the “reductionist” approach which treats classification of living organisms as a “convergent” problem i.e. there is a single solution which will be found if we have looked at it in sufficient detail. In my considerable experience with Oxalis, I found that morphological detail did not greatly help at understanding the genus in terms of a realistic species concept (see Part 1). This is because the variability and continuities are so extensive over so large an area, and so subtle, that it is virtually unmanageable. To suggest that cytology (and similar technologies) will contribute to the clarification of these vast grey areas, is asking too much of it. In my opinion cytology and a proper understanding of genetics and genes, will probably help explain why our classifications are improbable and difficult, rather than ease the task.
Meve’s revisions (1994, 1997) do not satisfy me at all. I put forward simple classification hypotheses for Duvalia and Piaranthus based on the same species concept defined in Part 1. Why is it that Meve did not set out to test those hypotheses in a systematic way. Technology should be used to test good judgement rather than present a solution which defies it. In Piaranthus, Meve has not addressed several critical issues which I had pointed out. In the case of the relationship between P. framesii and P. punctatus, he has created a bit of a farce. His discussion is very weak and his comment on the “single common habitat” (where both occur) is erroneous. My own breeding experiments showed that the element framesii and the element punctatus were fully compatible and I raised many seedlings. This in itself contradicts Meve’s report that the two elements are genetically incompatible. One of my very first observations was that the shape of the trichomes on the corolla was not diagnostic for framesii (Bayer & Plowes, 1975). Meve’s belief that it is, makes me doubt anything else he may have concluded. His illustration of the corona of framesii shows a dorsal crest (which he calls a wing-like projection). It should not be there at all in a true framesii and this was also an observation of mine. The type sheet has specimens with such a projection and some with none, as was the case in the ‘species’ described by Pillans. The type also never had the basal projection illustrated by Meve. What is odd is the terminology that Meve uses in describing one structure as two, in the ‘species’ in question. It is at variance with that given in his introductory discussion. He refers under framesii to wing-like projection along the filament tube ‘instead of a dorsal staminal corona’ (elsewhere called the ‘dorsal crest’). This is also absent in the type. In the single common stand (Bayer 423, 424) there were specimens with crests of every order and only one specimen that passed for framesii. I examined at least 17 plants from that locality. Meve must have wholly misread the article by myself and Plowes (1975). The coronal variation illustrated there should have given Meve considerable scope for thought, and he has instead obfuscated the situation completely. I should not have attached any significance to a short pedicel and I have to plead guilty to aberration which may have been in deference to my co-author. ‘We’ illustrated a range of variation between what was typically framesii (no dorsal crest at all) and typical punctatus (with dorsal crest). I have since observed another common stand and am confident that more diligent field investigation would show that the existence of common stands is an explorative rather than a biological function. The statement that the species are ecologically isolated is false (evident from the cited specimens) and simply a product of poor observation, inadequate collecting and misidentification. It is also a product of the unjustified belief that vegetation can be quantified and described as easily as the myth of discrete species. It appears from the revision that Meve has taken the original description of framesii and given it a completely different and wider application. But he does not give any indication that this was a cognitive decision. It is also almost certainly a bad one.
By his juggling of fact and fantasy, Meve misses the significance of the fact that framesii and punctatus may be con-specific (and I have no doubt that they are). The concept of framesii does stand as unique within the whole genus but not for the reason that Meve gives. It is unique because between punctatus and framesii (and within that one species), we have morphological differences which in degree exceed those on which genera could be based.
There are many other problems and it would be tedious to list them. One is the putative hybrid punctatusXcornutus at Kliprand (Bayer 440). As an identification of an herbarium specimen this could be a good guess. As the collector, and one who is familiar with Piaranthus (and with other genera and species) in the field, my reaction to my collection when I made it, was that it was indeterminate. There were no indications of either of Meve’s putative parents at the scene. A realistic assessment would have been that the collection indicated a fundamental weakness in the classification that needed further examination. Since then this intermediate has again been collected north of my locality and confirms the problem of intermediacy. The species barrydalensis could also be a problem. The statement that it is sympatric with geminatus var. geminatus is barely supported by the collecting data – if at all. Even less so if one recognises that some of the latitude/longitude grid references are cited incorrectly. I find a statement regarding stoutness of lobes, indumentum, flowering time, and stems to “show that we have to deal with a distinct entity” far too questionable and equivocal to be even reasonable. Meve also ignores other cases I mentioned where I had problems resolving the “species”. Meve failed to address these problem areas at all. As has happened repeatedly in Haworthia, he has taken the genus as a new problem that has to be solved. He should have of considered that a solution had been presented. This solution exposed problem areas that he should have addressed.
The presentation of the Duvalia revision is to a degree another matter and I must confess that I am generally more impressed. However, here I also have some problems. Meve certainly has not actually gained any better vision of the Southern African species than that which I presented. A closer look reveals many flaws. As it is I think my hypotheses for Piaranthus and Duvalia actually demonstrate that a good species concept can achieve just as much, and perhaps more, than an investigation backed by the most sophisticated technology.
Meve seems to have misunderstood my thoughts or statements about D. modesta and D. pillansii. The fact is that I generated plants of D. modesta from the seed which I produced by artificial pollination of D. pillansii. This is something that needed to be explained and explored. His statement that pillansii is a sister species to modesta is left unexplained. He says of modesta that it can be confused with caespitosa, and despite that says that the closest related species is pillansii. These are typical obfuscations one comes to expect in taxonomic treatments and my dissatisfaction still has its heart in something else. This is in the view that I find expressed regarding Haworthia, where it is often remarked that it is a genus in the state of ‘active evolution’. I find this statement nauseating because my experience with so many genera, including Duvalia and Piaranthus, is that the statement is true for all of them. When is evolution inactive? I can almost guarantee that give me any revision, and I will go into the field and find points where it breaks down completely and is inadequate. Meve says ‘separation of Duvalia species is not easy because there are only few good and non-quantitative characters’. Surely he means few quantifiable characters? Why did he not use a proper antonym for quantitative? He could as easily have said and meant non-qualitative characters? His statement is thus non-sensical. His problem is firstly that of an inadequate species definition which does not concede the continuity inherent in the concept of evolution and change. Secondly it is a product of the DNA/gene mythology where genes and characters are seen to determine characters in a linear, uni-directional and additive way (as required for a dichotomous key and a cladogram). The characters are there and all he is really saying that they do not fit a presence/absence scheme and the concept he has of the species! In the light of his statement about characters, the comment concerning D. caespitosa var. compacta is quite extraordinary.. “Like the typical variety but differing in a considerable number of sometimes cryptic features”. His secondary key (a little different from the main key) consists of five items and not one of them is exclusive. Thus what he should have said is that the differences between the two varieties is “weak” rather than “cryptic” (meaning “hidden”).
Meve further says that a quote from Stuessy ‘perfectly fits the species concept used in this study’. One is left to wonder if he has other species concepts for other occasions, and more consequently if his concept preceded the study or was derived from it. A quote of this kind is simply not good enough. Under caespitosa ,other than as given on the maps, there is no indication if the two varieties occur sympatrically or not. My experience is that they so often do (i.e. local variation within populations is so great) that it is impossible to maintain a taxonomic distinction. He has dealt with the specimens as individual collections and there is very little indication that he has really considered variability within populations. If he had done so it is very likely that his perceptions of Duvalia caespitosa, D, vestita and D. pubescens could have been different. I can almost guarantee that I could produce flowers of the species caespitosa, vestita, pubescens, modesta and even corderoyi which no one could separate with any confidence at all. I really doubt on the basis of my own experience, that the specimen citations as they are, could be replicated. Furthermore I am convinced that re-collections from the same localities, would in many cases be conflicting with the identifications he has made.
There is a curious incongruence in his complaint about ‘non-quantitative’ characters. Quantitative characters should be more determinate and manageable than qualitative characters. Where he uses quantitative characters one would expect easier judgements. This does not seem to be the case. Meve uses height of annulus as a character but does not seem to correlate this with the general size of the flower. There is actually a major problem in the field of separating the two varieties of caespitosa from each other and from D. modesta. A specimen from Matatiele (far to the north-east) is identified as modesta and Meve has given the chromosome count as 2n=22. That is right for the species, but the specimen cannot be modesta if the height of the annulus or lobe replication are considered . The specimen is caespitosa which should have 2n=44. Similarly there are two collections from Cradock and Pearston which contain both modesta (non-replicate lobes, low annulus) and caespitosa (replicate lobes, high annulus) and Meve has identified both as modesta. His chromosome counts for Pearston are 2n=22, but he has not addressed the problem the herbarium sheets present. I am left to wonder if D. modesta is not in fact the diploid form of D. caespitosa. The two species are perfectly compatible in that cross-pollination produced fertile seed and seedlings. What was the ploidy level of the offspring? This is somewhat of a mystery to me because Meve has made much of ploidy levels. He presumes hexaploids to have arisen from doubled triploid chromosome sets. Where are the triploids?
There is a similar problem in the Riversdale area involving vestita and elegans. The variety of elegans (var. seminuda) is identified as elegans and the specimens shows that it must co-occur with vestita. Their similarity is so obvious that the logical thing to do is to question the ploidy level where vestita is claimed to be 2n=44, and elegans 2n=22. He also suggests that fire may have something to do with the rhizomatous nature of the stems. How would he explain then the very rhizomatous stems of say Stapeliopsis breviloba or Tromotriche thudichumii which occur in an entirely fire-free habitat. Extrapolated to other species, the statement is completely frivolous, and it is in any case very dubious for even the species concerned. The southern Cape vegetation is in general very fire prone, but there are extensive arid, or sometimes island-like habitats, which are not affected by fire at all.
Meve has produced a ‘better’ revision of Duvalia than he has of Piaranthus. The two revisions are the assemblage of a great deal of information and an impressive quantity of data which is probably impregnable to the ordinary glance. The resolution of the species within the genera is similar. Thus for example while D. parviflora is very localised and discrete, D. caespitosa is not; P. parvulus is localised and discrete, P. geminatus is not; in Duvalia it is relatively easy to recognise at least 9 of the 13 species, in Piaranthus it is easy to recognise 4 of the 7 species. I have looked at them critically like this to show that, as works of science, they can be questioned and are refutable. The question of art does not arise even though there are many points which can be shown to be poor science. If the other genera are revised on the same basis and applying the same ‘level’ of judgement and quality of interpretation’, the prospects for say Stapelia and Huernia may not be good.
A weak revision which is accepted and passed by the watch-dogs of science, detracts from the credibility of any other revision. Unfortunately it is very difficult for peer-review to operate in plant taxonomy. What review does take place may be relevant to aspects of genetics or morphology but not to the actual object of the classification viz. the species. Imposture becomes all too easy. Revisions which do not properly review and address existing hypotheses are a serious liability and can bring classification into disrepute. I have no wish to hurt or offend Dr Meve, but the fact is that his revisions in a small way do just that, and so may actually contribute to the invalidation of others who also have an honest contribution to make. Such contributions may be seen as dubious works of art or simply be regarded as superficial opinions which are so aptly described as ‘vain thoughts’.
My conclusion thus is that a classification is an hypothesis which is based on the facts as they are presented by the herbarium, the written and the pictorial record. The concept of a species, on which there is a vast literature, has to be understood. It has to be reduced to a simple definition which applies to the entire spectrum of biological diversity. Reasoning and logic must be applied to the facts to arrive at a classification. Such a classification can be tested against new records (facts) and lead to a new hypothesis. In this way there is no place whatever for the notion that taxonomy is an art, and the idea that it is a simple “matter of opinion” becomes completely non-sensical. There is a real problem, that in the field of amateur and semi-popular literature, there is little understanding of the weaknesses in science, and scepticism is correspondingly disorganised and often mis-directed.
- Bayer, M.B. & Plowes, D.C.M. 1975. Some Stapeliads of the southern and south-western Cape. 1. Piaranthus. in Excelsa 5:71 (1975).
- Capra, F. 1982. The Turning Point. Simon and Schuster, USA.
- Lavranos, J.J. 1998. Letter to the Editor. Asklepios 73:3-4.
- Meve, U. 1994. The genus Piaranthus. Bradleya 12:57-102.
- Meve, U. 1997. The genus Duvalia. Springer Verlag. Vienna.
- Schumacher, E.F. 1980. A Guide for the Perplexed. Abacus.
- Spearing, J.K. 1998. A preliminary study of the morphology of seedlings of the genus Duvalia. Asklepios 75:28.
- Walker, C. 1997. Asklepios 72:12-13.