Biology as a science consists of two major approaches to the study and understanding of living organisms. The first approach is largely experimental and reductionist. It is mostly interested in trying and finding general laws and phenomena that apply to all or many organisms. These include molecular, genetic, developmental or physiological aspects of biological reality. Individual organisms used in such studies are just understood as “material” or “models” for establishing results that can be extended to many or all other organisms, and their individual characteristics, that cannot be generalised, are perceived as an irrelevant “noise” rather than as a matter of scientific research. In contrast, the second approach to biology, which is largely holist, comparative and mostly based on observation, is mainly concerned with variability and change among and within living beings. The term systematics applies to this approach, which deals with the diversity of organisms, their relationships and evolution [15–17]. Under this approach, unique characters of some kinds of organisms (species or higher taxa) are not considered as a meaningless “noise”, but rather as the basic facts on which our understanding of relationships and evolution is based.

Systematics itself consists of several complementary but distinct disciplines, that include taxonomy (the inventory and classification of the kinds of organisms), cladistics (the study of genealogical relationships between the latter units) and “evolutionary biology” (the study of the modalities and causes of organismal evolution, including historical biogeography). In the recent decades, the last two disciplines have been largely flourishing, while taxonomy has suffered a continuous, and ultimately dramatic, decline in prestige, resources and number of professional positions. The causes of this decline are several and probably more complex than has been stressed until now.

Some biologists think that we only need to study a few species of organisms, either because these “models” would be enough to know all about life, or because only those species that are directly useful or harmful to mankind are worth studying and, if threatened, protecting (e.g., [18]): although they probably play a significant rôle in the disaffection of many for taxonomy, such attitudes are inexcusable as they ignore the absolute need of taxonomy, both for a basic understanding of biodiversity and of its evolution, and for many social uses, a need which has been largely documented (e.g., [5]). Some other biologists, in a regularly decreasing number however, simply think that most of the taxonomic activity has been completed since Linnaeus' time, that a grossly acceptable knowledge of the biodiversity of our planet is now available, and that only minor adjustments are still necessary, thus fully ignoring the taxonomic impediment.

Such attitudes, in fact, often have a very material, not ideological, basis. It is a simple and general ecological law that any increase in the number of consumers, not being associated with an increase in resources, leads to an exacerbation of competition among consumers. The same applies to systematics as a whole in the last decades. In many institutions, such as, e.g., the major museums, the resources in terms of budgets and professional positions available for systematics have remained stable or have declined, while new disciplines have developed, such as cladistics or molecular evolution, no doubt at the expenses of the older field of taxonomy. Tenants of the new disciplines have clearly had a much more aggressive attitude than the leaders of taxonomy, and, quite importantly, they have been able to speak a language closer to that of other biologists, thus convincing them of the need to support their works, however without increasing the total resources allocated to systematics as a whole (which clearly would have been the logical course but would have required a common mobilisation of all systematists and evolutionary biologists, rather than a corporatist attitude of some against the others).

On the other hand, a basic characteristic of taxonomy is the importance of its descriptive, observational and comparative components, that require more manpower and meticulous daily activity than the recourse to experiments, sophisticated techniques and highly speculative approaches. No doubt the extraordinary recent development of the cladistic methodology, and its considerable impact on systematics as a whole (e.g., [5]), has had a major negative impact on taxonomy. This is partly because, for many scientists today, taxonomy being mostly descriptive, it is no more part of science itself: “les paradigmes et les modes de fonctionnement de la science tendent à rejeter les aspects descriptifs à l'extérieur du champ de la recherche scientifique, pour n'y retenir que les aspects conceptuels, historiques et explicatifs” ([19], p. 5). Strangely, this idea that observational data are not part of science seems to be shared by many scientists nowadays, although such descriptive data, that are meant to reply to “what?” questions, are the indispensable basis for any further scientific research, and must be addressed before “why?” and “how?” questions can be considered [17]. Interestingly, in other fields of research, descriptive works are not facing the same problem, much to the contrary: various very costly research programs, such as, e.g., those dealing with nucleic acid sequencing (including the Human Genome Project but also all works in molecular phylogeny) or many space research programs, are also purely or largely descriptive but are nevertheless considered prestigious and receive major fundings. One possible explanation of this discrepancy may be that all these programs require the use of very costly equipment and materials, so that a large part of their funding is “reinjected” from scientific research into technology and industry: these programs may thus be perceived as “economically fruitful”, even if their scientific results, in the short run at least, cannot be considered as such. In contrast, taxonomic research is mostly in need of manpower, intellectual competence and working time, i.e. professional positions, contracts and salaries, and may therefore appear by purely economic standards as only a cost without benefits.

The recent use by some cladists, to designate cladogram-based classifications or “cladifications” [17], of the formula “predictive classifications” (e.g., [19], p. 3), probably has had another negative impact on the perception of taxonomy by outsiders of this field. This formula is inadequate as it may suggest, at least for superficial readers, that such classifications already contain all the necessary information on all organisms, including those that are still unknown to us, and may exempt us from the need to continue to study them. As a matter of fact, the predictive power of such classifications only concerns the past, not the future, and the possible predictions mostly concern correlations between characters. Our knowledge of the characters of some organisms may indeed provide information on the characters of their ancestors and of their close relatives, and on the associations of characters in these organisms, but on the other hand the information obtained on the ancestors does not tell us anything about their descent. The study of the giraffe and its comparison with other artiodactyls may allow us to “predict” that their ancestors included species with shorter necks, but the discovery of the okapi could in no way have allowed us to predict the existence of giraffe if the latter had been unknown: the ancestors of okapi and giraffe could have given birth to many other descendants, of course inside a range of possibilities limited by a number of constraints, but only the real events that actually occurred during the evolution of this group, and which were not predictable before their occurrence, have a real interest for the biologists of evolution. In other words, there exists no such thing in organic evolution as a Mendeleev table of living species. Taxonomy is a science of real organisms, as they are observed and analysed by us, not of potential or hypothetical organisms or ancestors, let alone of hypothetical genealogical relationships between the known organisms: the study of the latter is the matter of another discipline of systematics, cladistics, which is complementary rather than contradictory to taxonomy in order to understand the diversity of organisms on our planet.

By its very nature, taxonomy is an individualistic activity. Whereas some parts of systematics, such as experimental approaches to evolutionary mechanisms or molecular cladistics, can efficiently be performed by research teams, as in most other scientific disciplines, the collective activities in taxonomy are mainly restricted to field work for collection of specimens and to some parts of the analysis of data (including phenetic and cladistic analyses), but the basic work of character analysis, of specimen and species descriptions, and of nomenclature, are mostly individual work. Furthermore, despite the wishes of some [20], taxonomy is not for the time being, and probably will not be for a long time still, a “unitary” discipline, as different schools of thought do exist, with different rationales, e.g., for the recognition of species or for the construction of classifications [15–17] or for the philosophical foundations of taxonomic nomenclature [21]: for the time being, no consensus exists between the competing schools, and imposition of a “unitary” taxonomy and nomenclature would certainly result in “cliques” imposing their views on classification ([20], p. 19). A “unitary” taxonomy could only be obtained through power relations between scientists, authoritarianism and censorship of adverse opinions, a course that has always proved to be disastrous for the progress of science, and bound to fail in the long run. In the coming century, taxonomy is likely to develop still major conceptual and methodological changes, particularly through the consideration of completely new kinds of information (e.g., [22–24]), so that no “final”, “stable” and “unitary” taxonomy can seriously be thought of in the short run.

Being a mostly individualistic discipline, it is not surprising if taxonomy attracts a number of individualistic personalities, and until now taxonomists have failed to organise themselves collectively, be it to defend their own professional activity. In most other scientific fields, including other disciplines of systematics, specialists have grouped themselves in associations, which publish journals and tend to act as lobbies to promote their discipline and defend their members, but taxonomists have failed to do so: there exists no international or national scientific society specifically devoted to the promotion and defence of taxonomy, and no journal devoted to publication of general papers on the discipline, its theoretical background, its history, its problems and its future. As a result, taxonomists as such are not represented, or are widely under-represented, in official or unofficial bodies that play a significant rôle regarding scientific policies, budgets and definition of priorities.

No doubt if such a lobby of taxonomists were to appear, one of its first actions should be to work for the development of a system of evaluation of the quality of research appropriate for the field of taxonomy. For the time being, in many countries and scientific institutions a large part of this evaluation is made through the use of “impact factors” (IF) as calculated by the ISI (formerly Institute of Scientific Information). However, impact factors do not provide a meaningful measure of the quality of taxonomic works, for several reasons including the long-term relevance of such works, the low number of specialists and the dispersion of papers in a high number of journals, many of which are not covered by the ISI [25]. Although the inadequacy of IF as a valid estimate of the quality of taxonomic publications is more and more acknowledged (e.g., [26]), for the time being no other method for such an estimate is widely accepted, a major problem that will have to be remedied soon if the status and prestige of taxonomy with regard to other fields of biological research is to be significantly modified.

An inescapable consequence of the preceding statement is that there is no real correlation between the scientific quality of taxonomic works and the IF afforded to the periodicals where these works are published. This has two corollaries: (C1) high quality, professional, taxonomic works can be and are regularly published in periodicals not covered by the ISI, or having low or very low IF; (C2) low quality taxonomic works, or works containing severe methodological taxonomic mistakes, can be and are regularly published in highly-ranked periodicals. Such “severe methodological mistakes” include unacceptable errors in the use of taxonomic concepts or methods (e.g., concerning taxon definition, diagnosis or delimitation, or the use of taxonomic hierarchy) and/or with regard to the international rules of nomenclature (ignorance of an earlier available nomen for a newly recognized taxon, failure to study the onomatophores of supposedly closely related taxa, ignorance of various articles of the relevant code, etc.). In this respect, it is important to stress that, regardless of the recent development of international discussions about some of the basic rules of the codes (e.g., “usage” versus priority as the fundamental structuring principle of nomenclature), or even on the basic philosophy underlying the mode of allocation of nomina to taxa (e.g., using “phylogenetic definitions of nomina” versus using onomatophores or nomen-bearing types) [14,21], for the time being, and until they are officially changed, the existing international codes of nomenclature [27,28] have a binding strength on all biologists worldwide and should be strictly followed in all scientific publications, including those with high IF!

As for evidence of the (C1) kind above, examples are too numerous, in all fields of taxonomy, to require documentation. Actually, most of the major taxonomic works cannot be published in periodicals indexed by the ISI, for the mere reason of their length: taxonomic revisions of genera and families, which are the basic reference works in taxonomy, are usually too long for most such periodicals, and can only be published in museum periodicals and monographs, none of which is covered by the ISI.

Concerning the statement (C2) above, it may seem surprising and it needs to be documented. Despite the widely held belief that highly-ranked periodicals do not publish taxonomic works, actually they do. In most cases the papers published in such periodicals are not centered on taxonomic questions, but quite frequently some works that deal with various questions such as molecular or morphological cladistics, or with evolutionary, genetic or ecological matters, may have taxonomic outcomes which are considered, or quite often “incidentally tackled” as a side effect of the research, in the course or in the conclusions of the paper. What is striking then is the high number of severe taxonomic and/or nomenclatural methodological mistakes (as defined above) that are currently published in various highly-ranked periodicals or books, some of which are even specialised in systematics or evolutionary biology, and although the authors of some of these works are very competent and respected biologists. A number of recent examples of errors in amphibian taxonomy and nomenclature were analysed in detail elsewhere [14,29–46]. Examples of taxonomic mistakes ([reference to error]/[reference to correction]) include the gross misidentification of well-known species ([47]/[37]; [48]/[40]), the description of so-called new species with inaccurate characters and referred to a wrong genus, if not subfamily and family ([49]/[40]; [50]/[46]), or, on the contrary, the failure to recognize a new species although clear characters were provided that should have led the author to do so ([51]/[36,52]), or the proposal of a new status (e.g., raising or downgrading of rank) for a taxon without discussing the status of the closely related taxa that are unavoidably affected by this change ([53–55]/[41]; [56]/[45]). Among the most noteworthy nomenclatural mistakes, let us just mention the erection of new taxa without providing a diagnosis, an onomatophore and/or a list of content, thus creating nomina nuda ([57]/[41]; [58]/[44]), the proposal of unwarranted new nomina for taxa already clearly nominated ([59–61]/[31]; [62–64]/[32,36]; [65]/[41]; [66]/[33,36]; [67]/[34]; [68]/[38]; [69]/[39]), or the gross misunderstanding of some basic provisions of the zoological code ([70]/[30]; [71]/[35]; [72]/[14]). The errors just listed appeared in various publications, including periodicals with low to high impact factors, e.g., Tropical Zoology (IF 0.233), Amphibia-Reptilia (0.506), Journal of Herpetology (0.562), Herpetological Journal (0.717), Herpetologica (0.757), Copeia (0.880), Zoologischer Anzeiger (0.893), Ethology, Ecology and Evolution (0.948), Zeitschrift für zoologischer Systematik und Evolutionsforschung (1.089), Zoological Journal of the Linnean Society (1.347), Molecular Phylogenetics and Evolution (3.345), Systematic Biology (6.239) or Science (23.872).

The repetition of such mistakes in such high-quality periodicals, where the closest attention is usually paid to most other aspects of the content (relevance of methodology to the question studied, rigour of experimental work and of its analysis, validity of conclusions, etc.), is significant of a general attitude of neglect for the taxonomic and nomenclatural aspects of work in biological research nowadays, even in the various other fields of systematics and evolutionary biology. Quite possibly, in the eyes of many biologists, even so-called “evolutionary biologists” or “phylogeneticists”, taxonomy and nomenclature are not really part of science, they are at best “techniques” of little interest and importance, and at worse they can simply be mastered through the simple use of “common sense”, without special knowledge and experience [14].

Poor quality taxonomic works have long been published, inasmuch as taxonomy has seldom been treated as a recognised academic discipline and has rarely been taught in universities, and as a number of contributions to the progress of the discipline have been provided by amateurs (which has always been necessary given the insufficient number of professional taxonomists). However, the recent multiplication of gross taxonomic mistakes in publications, including highly-ranked ones, is witness into a situation of strong dereliction for this discipline. This is doubtless related to the current underrating of the latter among biological sciences. Many young biologists and students are at first intellectually attracted by taxonomy, but they soon realise that this discipline is not very “promising”, so that at least the best of them tend to leave it for other fields of biology that are more attractive in terms of individual career: if this process continues for long, it is to be feared that many excellent biologists will refrain from entering taxonomy, thus reinforcing the negative image of the discipline conveyed by some. The paucity of academic training courses, not in “zoology” and “botany” in the traditional sense (i.e., descriptive knowledge of the major groups), but in the conceptual and technical bases of taxonomy and nomenclature, also contributes to this ignorance of the discipline.

Changes in this respect will be possible only when the relevance and importance of taxonomic completeness and accuracy is recognised by non-taxonomist biologists. Among the latter, conservation biologists may play a significant rôle, as their discipline needs sound taxonomic bases, and they should feel primarily concerned by the need to reduce the taxonomic impediment. An “alliance” between taxonomy and conservation biology would seem highly justified on several grounds: conservation biologists need taxonomic knowledge to act efficiently, and taxonomists are highly concerned by the accelerated extinction of their basic object of study, living species. However, this “natural alliance” is currently wanting, for several reasons that should now be considered.

Conservation biology as a whole (i.e., not limited to a few well-known “flag species”) cannot be thought of without sound taxonomic bases. Our current taxonomic survey of the living species of the planet is much below the needs, both as concerns taxonomic completeness and taxonomic accuracy. Conservation biology needs to support taxonomic work as a necessary basis for its own efficiency.

Let us just consider one example, taken in a long explored area (Europe) and a well-known group of rather large animals (frogs). In 1960, zoologists considered that only two species of “green frog”, Rana esculenta and R. ridibunda, occurred in Europe [73]. Less than forty years later, in 1996, the taxonomic status of the European populations of green frogs had been re-examined and the number of species recognised by taxonomists had risen to twelve [36] – and this is probably not the last word on this question. Such an example is by no means exceptional, it rather corresponds to a general situation in zoology, in almost all taxonomic groups and all regions of the planet. Of course, when what was considered to be two species turns out to be twelve species or more, this has considerable impact on our understanding of the evolution of the group, and on our statements about distribution, endemism, and threats to populations (e.g., [74]). The same holds true in many other cases: without a sound taxonomic basis, it is often difficult to take appropriate conservation decisions. However, for many conservation biologists, “conceptual changes in systematics are often viewed with suspicion, particularly if these may lead to the recognition of numerous additional species” ([75], p. 579).

To tell the truth, a number of conservation biologists do not pay much attention to taxonomic problems, in part because they probably share some of the negative appreciations on taxonomy mentioned above, and in part because, quite contradictorily indeed, they think, or would like to think, that our current taxonomic survey of biodiversity is largely satisfactory. As a result, they deal with taxonomic lists of species very much like administrative bodies or various non-biologist users of species lists, as if these lists were final and definitive. However, the request for stability of lists of nomina “is not a scientific demand, as the permanent evolution of science very often requires modification of what was once believed to be true or right” ([36], p. 5).

Strangely enough, besides claiming their lack of interest in taxonomy, a number of conservation biologists show a naive and unwarranted confidence in the validity of published taxonomic data, even if these have not been recently revised: they may then accept fully and “blindly” (i.e., without critical evaluation) some of the statements made, sometimes long ago, by a few taxonomists. For example, if a species has been traditionally divided in several subspecies in the past but no recent re-examination of the status of the latter has been done recently using modern methods and concepts, uncritical use of the mere nomina of these subspecies as an evidence for homogeneous genetic and/or taxonomic units may be completely misleading. If these are taken as basis for decisions regarding, e.g., their placement in lists of threatened taxa, or reintroduction of specimens after extinction, or conservatory measures concerning habitats, these decisions may be completely irrelevant. Similarly, all statements dealing with geographical distribution of species, which are often important in conservation biology, run the risk of being partly or completely wrong if they are based on an obsolete taxonomy or on incorrect species identifications [37,76]. Ideally, any conservation biology action should be undertaken only after a revision of the taxonomic information.

By ignoring the need of a recent revision of taxonomic data as a preamble to their actions, conservation biologists are therefore running the risk of taking inadequate decisions. This is one side of the problem of the relationships between the two disciplines. The second side is the risk for conservation biology to act as an efficient brake against the development of taxonomic works.

The problem at stake here is connected with the collecting of specimens in the field for taxonomic work. For several centuries, collection of animal and vegetal specimens was made without any special care and without any legislative constraints. In the recent years however, and mostly as an outcome of the Rio de Janeiro conference, more and more constraints have developed for such collecting, and for international transfer of specimens between countries.

The historical background of this evolution is important to consider. For a long time, although a major part of the earth's biodiversity is concentrated in the intertropical zone, very few biologists were working in this region, and most of the taxonomic studies of biodiversity were carried out in Europe and later in North America. The major developments of taxonomy accompanied the spreading of western colonisation of many tropical countries: in the 18^th, 19^th and early 20^th centuries, millions of specimens were collected all around the planet by naturalists who accompanied military expeditions and by westerners settled in the colonised countries. These gigantic collections, mainly stored in the major museums of Europe and North America, were the fundamental basis on which developed our understanding of the many aspects of species biodiversity on our planet, of the major characteristics and distribution of the taxonomic groups, and of the fact and modalities of biological evolution. In the 20th century however, with the progresses of decolonisation, many tropical countries became more and more concerned with “their” biodiversity being studied by others. They expressed interest in studying it locally, and in having their own museums and collections. More recently, and mostly after the Rio conference, a set of legislative and juridical texts developed, which progressively established a “biodiversity protectionism”: it is now more and more difficult for biologists to obtain official permits allowing them to study biodiversity in countries other than theirs, or even in their own country. Even more than for mere study (e.g., behavioural or ecological observations), it is now increasingly difficult to get permits for collecting specimens and exporting them back to the country whence the researcher came, or to loan them from one country to another.

In the light of the past, this attitude of many tropical countries is fully understandable. Whether it is really justified and adequate with respect to the aim officially announced by them, i.e. to study and protect their biodiversity, is more questionable. Most unfortunately, but undeniably, many of these countries are currently unable to sustain alone heavy taxonomic surveys of their biodiversity, to create and fund large museums where long-term conservation of millions of specimens can be guaranteed, and to implement ambitious conservation plans for threatened taxa and biota in their territories. In this respect, stopping or seriously limiting such works by foreigners may simply result in extinctions continuing to increase, especially following deforestation and other habitat changes, without any study to evaluate these losses and possibly to propose some conservation measures for particularly threatened taxa and biota.

Actually, the idea that biodiversity is a “property” of the human inhabitants or of the country where it occurs, although historically and socially understandable, is open to discussion. An alternative way to see this question could be to consider all the biodiversity of our planet as a natural richness for which mankind as a whole has the responsibility to care, i.e. a collective heritage of all humans. Under such an interpretation, biodiversity protectionism would have no justification, but it would rather be the responsibility of all States to take all needed steps to allow proper study and conservation of their biodiversity, including if necessary by the recourse to collaborative research and conservation programs involving foreign scientists, experts, technical and financial help. However, it may well be difficult to pass such a message around, if, under the cover of fighting against the remains of colonisation, such countries do indeed pursue other aims, including purely financial ones. One of the conclusions apparently drawn by some from the Rio conference is that biodiversity now has a value, not only patrimonial, biological and cultural, but also purely financial. Some States may feel that, if organisms or their molecules can be patented, they may be an unexpected source of financial resources, and that access to them should be strictly restricted, or that this access should be charged. This is actually what is more and more often observed, sometimes under the cover of official “collaborative programs” or, locally, of “buying souvenirs”. This attitude may be caricaturally illustrated by this image of a biologist from the “North” counting the banknotes with which he will buy zoological specimens in a tropical country, with the following legend under the photograph: “If we don't buy them, they'll be eaten” ([77], p. 89).

Acknowledging the importance of good taxonomic works as a basis for adequate conservation biology programs leads to the conclusion that conservation biologists should support the claim of taxonomists for obtaining good conditions to carry out their research work, i.e. the possibility to collect in the field, not only one or two, but real series of specimens (as most taxonomic works rely on statistical treatment of data), to kill and fix them properly, and to have later access to them for study and for comparison with other series of specimens of supposedly close species. This does not mean that the specimens should necessarily be deposited in some other country, but at least that it should be possible to export them temporarily for study and comparisons with other museum specimens. Such loans of zoological or botanical specimens are routinely done between natural history museum of the “North”, but are much more unusual between the latter and tropical countries' academic institutions and collections.

In the recent years, many taxonomists have had the feeling that they were not receiving from their colleague conservation biologists the help they would consider normal to support their requests for collecting series of specimens in the field in order to ascertain the taxonomic status of some populations. Rather, they have often found these colleagues in front of them, supporting the most restrictive legislative provisions that tend in fact, in many countries, to limit considerably, if not fully impede, taxonomic work based on recent field data. This is all the more surprising as, in a vast majority of these cases, the ban on collecting was not based on any scientific appraisal of a risk that the collection of a series of specimens could bring to the populations at stake: actually, such a risk is impossible to ascertain before any study of the populations. An a priori negative position in this respect tends to resemble more a “fundamentalist anti-scientific” attitude than one based on a serious analysis of problems. Time should now come when conservation biologists tend to behave fully like scientists rather than like militants for the prevention of cruelty to animals: no scientific assessment of threats posed to biodiversity is possible without first a taxonomic evaluation of the taxa involved, and conservation biology should consider taxonomy as its indispensable ally, not as its enemy.