Names,numbers and indentations: a guide to post-Linnaean taxonomy

The vast majority of biological taxonomists use the Linnaean system when constructing classifications. Taxa are assigned Linnaean ranks and taxon names are devised according to the Linnaean rules of nomenclature. Unfortunately, the Linnaean system has become theoretically outdated. Moreover, its continued use causes a number of practical problems. This paper begins by sketching the ontological and practical problems facing the Linnaean system. Those problems are sufficiently pressing that alternative systems of classification should be investigated. A number of proposals for an alternative system are introduced and evaluated. The best aspects of those proposals are brought together to form a post-Linnaean system, and a comparison of the Linnaean and post-Linnaean systems is conducted. The final section of this paper considers not only the theoretical reasons for replacing the Linnaean system, but also the practical feasibility of adopting an alternative system.     

Towards a new classification of Leguminosae: Naming clades using non-Linnaean phylogenetic nomenclature

The past three decades of research have greatly advanced our understanding of phylogenetic relationships in the family Leguminosae. It has become clear in recent years that our classification system is in need of significant updating if it is to reflect our current understanding of the phylogeny of the family and facilitate effective communication of that knowledge. The goal of this paper is to suggest a set of guidelines for formally defining and naming clades, which draws on many of the recommendations embodied in the draft International Code of Phylogenetic Nomenclature or “PhyloCode”. I provide specific examples of phylogenetic nomenclature applied to several well recognized and well-supported, informally named papilionoid clades to serve as a model for standardizing legume clade names by the legume community in the future. For the most part the clades named here are below subfamily and above tribal ranks in the Linnaean system. It is my contention that a new Linnaean classification, designed to reflect phylogeny, and a clade-based system of phylogenetic nomenclature are mutually complementary approaches to achieving a new classification of the legume family.     

Forum – Taxonomic Stability is Ignorance

Absolute nomenclatural stability is undesirable in phylogenetic classifications because they reflect changing hypotheses of cladistic relationships. De Queiroz and Gauthier's (1990: Syst. Zool. 39, 307–322; 1992: A. Rev. Ecol. Syst. 23, 449–480; 1994: Trends Ecol. Evol. 9, 27–31) alternative to Linnaean nomenclature is concluded to provide stable names for unstable concepts. In terms of communicating either characters shared by species of a named taxon or elements (species) included in a taxon, de Queiroz and Gauthier's system is less stable than the Linnaean system. Linnaean ranks communicate limited information about inclusivity of taxa, but abandonment of ranks results in the loss of such information. As cladistic hypotheses advance, taxa named under de Queiroz and Gauthier's system can change their level of generality radically, from being part of a group to including it, without any indicative change in its spelling. The Linnaean system has been retained by taxonomists because its hierarchic ranks are logically compatible with nested sets of species, monophyletic groups, and characters. Other authors have offered conventions to increase the cladistic information content of Linnaean names or to replace them with names that convey cladistic knowledge in greater detail; de Queiroz and Gauthier sacrifice the meaning of taxon names and categorical ranks in favor of spelling stability.     

Is the Neotropical flora ready for the PhyloCode?

Nomenclatural systems are structured around classification, and together they enable increasingly informed communication about biological diversity. Challengers of Linnaean classification and nomenclature have proposed the PhyloCode, a new set of rules that would govern the way systematists classify and name the diversity of life. Monographs and floras are two fundamental vehicles for communicating information about plant diversity. These works provide a comprehensive foundation of botanical research upon which other scientific studies are based. Information conveyed by monographs and floras is utilized directly or indirectly both within and outside the scientific arena by a wide range of consumers, such as educators, agronomists, ecologists, conservationists, amateur naturalists, and even lawmakers, to name a few. Both classification and nomenclature are essential to the process of synthesis that leads to monographic and floristic treatments and the communication that they facilitate. Conversion to a new system would have far-reaching consequences for the flow of information from systematics to other scientific disciplines, and to society. The purposes of this article are to address the proposed conversion from the perspective of monographic and floristic research focused on Neotropical plant diversity and to point out some difficulties in applying the PhyloCode to the Neotropical flora. Although we welcome improvements in the current nomenclatural system, we conclude that the PhyloCode is not prepared to replace the Linnaean system as a new way to communicate information about Neotropical plant diversity.     

Classification of apocynaceae s.l. according to a new approach combining Linnaean and phylogenetic taxonomy

A new approach to a nomenclatural system, including elements from both Linnaean and phylogenetic nomenclature, is proposed. It is compatible with the existing Linnaean system, including "standard names" corresponding to principal and secondary ranks, and uses a variant of the definitions from the Phylocode system. A new infrafamilial classification, using this nomenclatural approach, of the Apocynaceae s.l. (i.e., including the Asclepiadaceae) based mainly on analyses of rbcL and ndhF data is discussed. Twenty-one tribes and four rankless taxa are defined.     

The Linnaean system and its 250-year persistence

The Linnaean system of nomenclature has been used and adapted by biologists over a period of almost 250 years. Under the current system of codes, it is now applied to more than 2 million species of organisms. Inherent in the Linnaean system is the indication of hierarchical relationships. The Linnaean system has been justified primarily on the basis of stability. Stability can be assessed on at least two grounds: the absolute stability of names, irrespective of taxonomic concept; and the stability of names under changing concepts. Recent arguments have invoked conformity to phylogenetic methods as the primary basis for choice of nomenclatural systems, but even here stability of names as they relate to monophyletic groups is stated as the ultimate objective. The idea of absolute stability as the primary justification for nomenclatural methods was wrong from the start. The reasons are several. First, taxa are concepts, no matter the frequency of assertions to the contrary; as such, they are subject to change at all levels and always will be, with the consequence that to some degree the names we use to refer to them will also be subject to change. Second, even if the true nature of all taxa could be agreed upon, the goal would require that we discover them all and correctly recognize them for what they are. Much of biology is far from that goal at the species level and even further for supraspecific taxa. Nomenclature serves as a tool for biology. Absolute stability of taxonomic concepts—and nomenclature—would hinder scientific progress rather than promote it. It can been demonstrated that the scientific goals of systematists are far from achieved. Thus, the goal of absolute nomenclatural stability is illusory and misguided. The primary strength of the Linnaean system is its ability to portray hierarchical relationships; stability is secondary. No single system of nomenclature can ever possess all desirable attributes: i.e., convey information on hierarchical relationships, provide absolute stability in the names portraying those relationships, and provide simplicity and continuity in communicating the identities of the taxa and their relationships. Aside from myriad practical problems involved in its implementation, it must be concluded that “phylogenetic nomenclature” would not provide a more stable and effective system for communicating information on biological classifications than does the Linnaean system.     

Homoplasy and the delineation of holophyletic genera in some insect groups

Abstract. Some groups of insects, such as certain Ichneumonidae and fungus-feeding Phlaeothripidae, appear to have undergone frequent reversal or parallelism (homoplasy) of characters during evolution so that extant species present almost every imaginable permutation and combination of characters. Recognition of holophyletic genera in such groups is difficult. Large monothetically defined genera are often not holophyletic, whilst small genera need to be defined by a large and invariable character-suite. Any classification produced by adopting small genera will not possess one of the valuable attributes of the classical Linnaean system, its predictive ability; a large proportion of new species will require new genera. For groups exhibiting a high degree of homoplasy it is suggested that a polythetic classification be erected. Polythetic genera can be holophyletic groups and are not merely phenetic assemblages. The probability of correctly assigning a species (either a new one or when making an identification) is shown to be higher for a polythetic classification. A simple key device, the polyclave, is given to enable practical separation of two polythetic taxa. It is suggested that homoplasy, and its associated problems in classification, may be associated with a particular type of biology in which population size is not limited by direct competition.     

Causes,kinds and forms

Realist philosophies of science posit a dialectical relation between theoretical, explanatory knowledge and practical, including taxonomic knowledge. This paper examines the dialectic between the theory of descent and empirical, Linnaean taxonomy which is based on a logic of traditional classes. It considers the arguments of David Hull to the effect that many of the practical problems of empirical classification can be resolved by means of an ontology based upon the theory of descent in which species taxa are regarded as individuals rather than as classes or natural kinds.Contra Hull, it is argued that this view is, at best, only partially consistent with taxonomic practice and that it cannot sustain experimental practice which presupposes that species taxa be regarded as natural kinds. An outline is given of a possible alternative dialectic between a field theory of morphogenesis and a rational systematics involving a logic of relations.     

The meaning of categorical ranks in evolutionary biology

Despite having been utilized for over 250 years, Linnaean ranks are periodically dismissed by some systematists and evolutionary biologists. Here, we discuss recent criticisms and point out that they are often the result of a misunderstanding of both the meaning and the intent of such ranks. Although arbitrary in some cases, ranks contain meaningful taxonomic information, facilitate communication, and serve as proxies for a fully resolved and correctly dated tree of life. Ranks favor communication and evolutionary comparisons, but they do not make assumptions about equal age or diversity for any two taxa with the same Linnaean category.     

淡水浮游植物功能类群分类法的提出、发展及应用

浮游植物分类方法是揭示浮游植物群落演替规律、开展淡水生态研究的工作基础和重要工具.林氏分类法和分子鉴定法在生态学应用上存在的不足促进了浮游植物功能类群分类法的发展.功能类群分类法是一种以浮游植物个体生态学为依据的生态分类法.本文概述了浮游植物功能类群(functional group,FG)、生态功能类群(morpho-functional group,MFG)和形态功能类群(morphology-based functional group,MBFG)等浮游植物分类方法的理论基础和分类依据,分析比较了这3种分类方法的优势与不足,认为FG是目前应用于水生生态学研究和水环境生物评价中相对适用的浮游植物分类方法.介绍了功能类群分类法在国内外淡水浮游植物生态学研究中的应用现状,简述了以FG为基础提出的Q指数法和Q-R指数法两种水质评价法的评价标准及存在的不足.
     

How to make oneself nature's spokesman? A latourian account of classification in eighteenth- and early nineteenth-century natural history

Classification in eighteenth-century natural history was marked by a battle of systems. The Linnaean approach to classification was severely criticized by those naturalists who aspired to a truly natural system. But how to make oneself nature's spokesman? In this article I seek to answer that question using the approach of the French anthropologist of science Bruno Latour in a discussion of the work of the French naturalists Buffon and Cuvier in the eighteenth and early nineteenth century. These naturalists followed very different strategies in creating and defending of what they believed to be a natural classification in zoology. Buffon failed, whereas Cuvier's work appeared to be very successful. My argument will be that, to explain Buffon's failure and Cuvier's success, we should not focus on the epistemological or theoretical concerns and justifications of these naturalists, but on the concrete and heterogeneous means or tools through which animals were mobilized, stabilized and combined into ever more comprehensive systems of classification.     

A Higher Level Classification of All Living Organisms

We present a consensus classification of life to embrace the more than 1.6 million species already provided by more than 3,000 taxonomists’ expert opinions in a unified and coherent, hierarchically ranked system known as the Catalogue of Life (CoL). The intent of this collaborative effort is to provide a hierarchical classification serving not only the needs of the CoL’s database providers but also the diverse public-domain user community, most of whom are familiar with the Linnaean conceptual system of ordering taxon relationships. This classification is neither phylogenetic nor evolutionary but instead represents a consensus view that accommodates taxonomic choices and practical compromises among diverse expert opinions, public usages, and conflicting evidence about the boundaries between taxa and the ranks of major taxa, including kingdoms. Certain key issues, some not fully resolved, are addressed in particular. Beyond its immediate use as a management tool for the CoL and ITIS (Integrated Taxonomic Information System), it is immediately valuable as a reference for taxonomic and biodiversity research, as a tool for societal communication, and as a classificatory “backbone” for biodiversity databases, museum collections, libraries, and textbooks. Such a modern comprehensive hierarchy has not previously existed at this level of specificity.     

Cytochrome b phylogeny and the taxonomy of great apes and mammals

In the Linnaean system of classification, the generic status of a species is part of its binomial name, and it is therefore important that the classification at the level of genus is consistent at least in related groups of organisms. Using maximum-likelihood phylogenetic trees constructed from a large number of complete or nearly complete mammalian cytochrome b sequences, I show that the distributions of intrageneric and intergeneric distances derived from these trees are clearly separated, which allows the limits for a more rational generic classification of mammals to be established. The analysis of genetic distances among hominids in this context provides strong support for the inclusion of humans and chimpanzees in the same genus. It is also of interest to decipher the main reasons for the possible biases in the mammalian classification. I found by correlation analysis that the classification of mammals of large body size tends to be oversplit, whereas that of small mammals has an excess of lumping, which may be a manifestation of the larger difficulty in finding diagnostic characters in the classification of small animals. In addition, and contrary to some previous observations, there is no correlation between body size and rate of cytochrome b evolution in mammals, which excludes the difference in evolutionary rates as the cause of the observed body size taxonomic bias.     

On the Other "Phylogenetic Systematics"

De Queiroz and Gauthier, in a serial paper, argue that biological taxonomy is in a sad state, because taxonomists harbor "widely held belief" systems that are archaic and insufficient for modern classification, and that the bulk of practicing taxonomists are essentialists. Their paper argues for the scrapping of the current system of nomenclature, but fails to provide specific rules for the new "Phylogenetic Systematics"—instead we have been presented with a vague and sketchy manifesto based upon the assertion that "clades are individuals" and therefore must be pointed at with proper names, rather than diagnosed by synapomorphies. They claim greater stability for "node pointing," yet even their own examples show that the opposite is true, and their node pointing system is only more stable in a purely metaphysical sense detached from characters, evidence, usage of names, and composition of groups. We will show that the node pointing system is actually far LESS stable than the existing Linnaean System when stability is measured by the rational method of determining the net change in taxa (species) included in a particular group under different classifications.     

The illusion of distribution-free small-sample classification in genomics

Classification has emerged as a major area of investigation in bioinformatics owing to the desire to discriminate phenotypes, in particular, disease conditions, using high-throughput genomic data. While many classification rules have been posed, there is a paucity of error estimation rules and an even greater paucity of theory concerning error estimation accuracy. This is problematic because the worth of a classifier depends mainly on its error rate. It is common place in bio-informatics papers to have a classification rule applied to a small labeled data set and the error of the resulting classifier be estimated on the same data set, most often via cross-validation, without any assumptions being made on the underlying feature-label distribution. Concomitant with a lack of distributional assumptions is the absence of any statement regarding the accuracy of the error estimate. Without such a measure of accuracy, the most common one being the root-mean-square (RMS), the error estimate is essentially meaningless and the worth of the entire paper is questionable. The concomitance of an absence of distributional assumptions and of a measure of error estimation accuracy is assured in small-sample settings because even when distribution-free bounds exist (and that is rare), the sample sizes required under the bounds are so large as to make them useless for small samples. Thus, distributional bounds are necessary and the distributional assumptions need to be stated. Owing to the epistemological dependence of classifiers on the accuracy of their estimated errors, scientifically meaningful distribution-free classification in high-throughput, small-sample biology is an illusion.     

Stems,nodes, crown clades,and rank‐free lists: is Linnaeus dead?

Recent radical proposals to overhaul the methods of biological classification are reviewed. The proposals of phylogenetic nomenclature are to translate cladistic phylogenies directly into classifications, and to define taxon names in terms of clades. The method has a number of radical consequences for biologists: taxon names must depend rigidly on the particular cladogram favoured at the moment, familiar names may be reassigned to unfamiliar groupings, Linnaean category terms (e.g. phylum, order, family) are abandoned, and the Linnaean binomen (e.g. Homo sapiens) is abandoned. The tenets of phylogenetic nomenclature have gained strong support among some vocal theoreticians, and rigid principles for legislative control of clade names and definitions have been outlined in the PhyloCode. The consequences of this semantic maelstrom have not been worked out. In pratice, phylogenetic nomenclature will bc disastrous, promoting confusion and instability, and it should be abandoned. It is based on a fundamental misunderstanding of the difference between a phylogeny (which is real) and a classification (which is utilitarian). Under the new view, classifications are identical to phlylogenies, and so the proponents of phylogenetic nomenclature will end up abandoning classifications altogether.     

Ecological periodic tables: in principle and practice

“Science is organized knowledge.” Immanuel Kant (1724–1804) Ecological periodic tables are an information organizing system with categorical habitat types as elements and predictably recurring (periodic) properties of a target biotic community, such as its relative species richness, abundance and biomass, as attributes. Ecological periodic tables are founded on the ecological tenet that habitats structure biotic communities and its corollary that habitats are templets for ecological strategies. They are a durable, open and flexible system that accommodates all operationally defined habitat types and biotic communities for which the periodicity of habitat usage patterns by a biotic community have been empirically substantiated. Discovering quantitative, periodic habitat usage patterns requires quantitative, representative, unbiased sampling of a biotic community across habitat types at ecologically relevant temporal and spatial scales. Like chemical periodic tables, the Linnaean system of classification and the Hertzsprung–Russell diagram in chemistry, biology and astronomy, respectively, ecological periodic tables are simple, easy to understand, exceptionally useful and they foster the expansion of scientific understanding, inquiry and theory.     

Typification of Brassica oleracea L. (Gruciferae) and its Linnaean varieties

OOST, E. H., BRANDENBURG, W. A. & JARVIS, C. E., 1989. Typification of Brassica oleracea L. (Cruciferae) and its Linnaean varieties. The Linnaean concept of Brassica oleracea and its varieties is discussed. In the light of this concept several types are considered and chosen.     

On the lack of good scientific reasons for the growing phylogeny/classification gap

An increasing number of phylogenetic analyses is no longer translated into classifications. The resulting phylogeny/classification gap is undesirable because the precise transmission of phylogenetic insights depends on the frequent revision of Linnaean names. The move away from classifying has numerous correlates. These include: an expanded pool of researchers who are able to produce phylogenetic estimates, a mismatch between the properties of molecular phylogenies and the requirements for verbal Linnaean definitions, the emphasis of statistical representations over the creation and evaluation of scientific terms, and a partial disconnect between the processes of nomenclature and taxonomy. The “taxonomic concept” approach allows systematists to express their varying perspectives with a high precision and can therefore help reduce the aforementioned gap. The phylogeny/classification link must persist in order to ensure community‐wide access to, and continued testing of, the products of systematic research. © The Willi Hennig Society 2005.