New Methods and Systematics: Two Erstwhile Items of Note

If it is not on the Internet, does it not exist? The Internet is becoming the primary mirror of human activity — from politics to pornography. Alas, our physical world, which gave rise to human civilisation with its chaotic ferment, was until recently reflected on the Web to a far lesser extent. Fortunately, progress has become apparent here as well. Databases of celestial bodies have been followed by virtual maps of the entire terrestrial surface. Next in line are the inhabitants of our planet. They will be encompassed by a networked project called the Encyclopedia of Life. Over ten years and (so far) 12.5 million dollars, a grand library is planned that will contain descriptions of all known species of organisms (1.8 million, according to the encyclopaedists). This publicly accessible database will become a most important source of scientific knowledge, will help track changes in the environment, and will kindle public interest in the diversity of life. The founders of the new encyclopaedia note that this year marks the three hundredth anniversary of the birth of the Swedish naturalist Carl Linnaeus, who laid the foundations of modern systematics. Indeed, this event would have given Linnaeus cause for satisfaction. Yet certain features of the new project might have troubled the scholar. Despite mountains of inscribed paper (and magnetised media, burned discs, and transferred gigabytes), we have still not understood what a species is. Species must be arranged not haphazardly, but systematically. The nature of this system likewise remains contested. Linnaeus himself devised two systems for plants: an artificial one (convenient to use) and a natural one (reflecting the inner essence). How to construct a natural system remains unclear to this day. Proclamations of victory issue from various camps, but no idea has earned — nor will it earn? — universal acceptance. Who, and by what means, will determine in the new encyclopaedia what is to be considered a species and what is not? In what order will these species be systematised and indexed? How will contentious nomenclatural questions be resolved? The team overseeing the encyclopaedia's compilation will consist of two to three dozen individuals representing authoritative scientific institutions of the United States and Great Britain. Will they prove equal to a task that thousands of systematists specialising in the study of individual groups of animals and plants have found beyond their reach — or will they simply skirt around the sharp corners? The aim of the new encyclopaedia is simultaneously magnificent and unattainable. To reflect by the efforts of a single team the labours and errors of the entire scientific community is a task of staggering difficulty. To contain the near-infinite diversity of life within the constricted space of species lists and taxonomic codes is impossible. That said, the most appropriate response to the problems enumerated above is to set about solving them — as the encyclopaedia's creators and their sponsors have done. The eyes may fear, but the hands will act. Notwithstanding all the difficulties, one can only wish the developers of the Encyclopedia of Life success. Yet another — and assuredly authoritative — source of information and species lists will come into being. That it cannot become the final arbiter is beyond doubt, but this does not diminish its value. For the time being, the public has been presented with specimen pages of the new encyclopaedia, containing text, photographs, maps, and video clips devoted to five species, among them the polar bear and rice. Regrettably, the page dedicated to Homo sapiens L., 1758 has not yet been written. We shall wait. Ciliates, butterflies, whales, and barcodes In early February, a conference on the collection of "barcodes of life" (Barcode of Life) was held in London. It addressed the launch of a grand biological project in which 50 researchers from 25 countries will participate. The objective is the creation of a publicly accessible database of nucleotide sequences of characteristic genes, provisionally termed "barcodes of life," for all organisms on Earth. It is anticipated that as a result, any DNA-containing material could be used to identify the species from which it was derived, by means of a procedure costing only a few dollars. The first phase of the project envisages the cataloguing of the mitochondrial gene cytochrome c oxidase of birds (approximately 10,000 species), fishes (approximately 15,000 marine and 8,000 freshwater species), and plants growing in Costa Rica (8,000 species). The resulting database is to be published in 2010. Explaining the project's objective, the authors state that thanks to "barcodes," a person lacking specialist knowledge will be able to reliably identify species. The point is that although identification keys have been developed for most groups, their use is not a straightforward matter. Different species differ from one another by different characters, which, moreover, one must know how to read¹. One old key from the British Museum contained approximately the following phrase: "It should not be forgotten that the results of species identification using the tables provided herein are of an approximate character, and the only reliable method is to consult a specialist in the relevant group of animals regarding the specimen of interest." Imagine having to reconcile oneself in our time — an era striving for unification and objectivity — with such a morass of difficulties. It is understandable why the mass media report on the Barcode of Life project with evident satisfaction. At last we shall bring order to the chaos of the living things around us! How convenient it will be when every species receives its own "genetic passport"! Let us nevertheless attempt to determine what this project can and cannot deliver. The concept of species seems very straightforward. When a naturalist sets out for a walk, he observes that living nature consists of clearly defined "sorts" of organisms — it only remains to find the characters by which they can be distinguished from one another. And if an amateur ornithologist may orient himself by plumage features or vocalisations, a professional cannot content himself with anything less rigorous than nucleotide sequences of mitochondrial genes. Those who cannot fully resolve what a species is are precisely the systematists who study species within their ranges. Let us consider but one classical example. In Western Europe there inhabit two readily distinguishable gull species: the lesser black-backed gull and the herring gull. Yet proceeding around the North Pole along the shores of the Arctic Ocean, one discovers that one of these species gradually transforms into the other — that is, a ring of subspecies girdles the pole. Between any two adjacent subspecies, interbreeding is possible and genetic material is exchanged, whilst the extreme forms are sharply delimited. There are no characters that allow a formal resolution of such a problem, and "barcodes" will not help here. It has long been understood that evolution proceeds unevenly with respect to different characters. Speciation may be the result of prolonged evolution with alteration of sequences in diverse genes, or it may occur within a short time through hybridisation or changes in chromosomal complement (highly characteristic, for instance, of fishes and amphibians). In insects, the emergence of reproductive isolation (the first step towards speciation) through infection with a particular bacterial species has been described. The outcome of all such processes — and many others — may be the existence of sibling species, for the recognition of which sufficiently complex methods are required. These are the species that the naturalist on his walk would not even suspect. Alas, for their delimitation, study of the cytochrome c oxidase gene may prove useless. These sequences may differ among individuals of the same species (for example, in the rather genetically uniform species Homo sapiens, several variants are known) and may coincide among different species! Hybrid species possess mitochondrial genes derived from the maternal parent during hybridisation, and changes in chromosomal complement do not affect mitochondrial DNA at all. This does not mean that DNA analysis will not help in the case of sibling species; it is simply that appropriate diagnostic characters must be selected. The situation is further complicated by the fact that different groups of organisms evolve in their own way. Some form well-differentiated species; others do not regard this as obligatory. The eminent Russian systematist Alexander Alexandrovich Lyubishchev remarked that the aspiration to create a universal theory of species applicable to all living beings is equivalent to the desire to devise tackle equally suited to catching ciliates, butterflies, and whales. Not knowing precisely what species are, the ambition to learn to recognise them by means of a single instrument is an even more impressive undertaking! The initiators of the project contend that the "barcodes of life" will help non-specialists identify species in the field. Let us examine how realistic this is, using the "pilot" group of the project — birds — as an example. We are assured that thanks to "barcodes," non-specialists will be able to monitor species diversity. But to do so, DNA-containing material would have to be obtained from all birds that appear unusual, which means the birds would have to be collected in some manner (killed?). Is this more efficient than employing a qualified specialist, who will almost invariably be able to identify birds by their appearance and sometimes by voice alone? Difficult cases will of course always arise. It is then that a contested specimen may be collected and identified using all available characters (including the cytochrome c oxidase sequence). Are there too few specialists? If a hare can be trained to beat a drum, a conservation officer can presumably be trained to identify birds as well. On 3 February, one of the founders of the biological species concept, the doyen of American ornithology Ernst Mayr, died at the age of one hundred. He pointed out that birds are the group of animals characterised by perhaps the most distinct differences between species. The indigenous peoples of New Guinea, who use neither binoculars nor field guides, distinguished (and had names in their own language for) the same bird species that highly learned ornithologists described (and named in the language of ancient Rome)! Incidentally, the task of nature conservation requires not only the recognition of rare species. Who will prove more capable of resolving diverse, often non-formalisable problems: the attentive naturalist-observer, or the specialist in reading "barcodes"? Thus, the Barcode of Life project will not be able to resolve the problems for which it is proposed. Does this mean that its implementation is without merit? Of course not. The project will yield a wealth of interesting and useful information. Its consumers will be qualified systematists, who maintain within their field of attention the entire — often contradictory — body of data on the characteristics of members of the group they specialise in studying. In any case, in the course of the project, data will be collected not only on the sequence of one single gene, but on many others of no lesser interest. Is such attention to the problems of describing species diversity justified? Certainly. For the author, as a biologist, this requires no proof. And to those who doubt, one may recall that according to the Book of Genesis, Adam in the Garden of Eden was occupied with giving names to the species of animals. How can we rest until this work is finished? ¹Do you know what character is used to distinguish merely three species of green frogs? The Tarashchuk index: the quotient obtained by dividing the product of the square of tibia length and the length of the longest toe of the hind foot by the product of the length of the additional tibia and the square of the length of the inner metatarsal tubercle. Most interestingly, the distributions of this value in related species still overlap to some degree. Back to text D. Shabanov. If it is not on the Internet, does it not exist? // Computerra, Moscow, 2007. — No. 19 (687) D. Shabanov. On the love of simple explanations // Computerra, Moscow, 2005. — No. 8 (580)

¹Do you know what character is used to distinguish merely three species of green frogs? The Tarashchuk index: the quotient obtained by dividing the product of the square of tibia length and the length of the longest toe of the hind foot by the product of the length of the additional tibia and the square of the length of the inner metatarsal tubercle. Most interestingly, the distributions of this value in related species still overlap to some degree. Back to text D. Shabanov. If it is not on the Internet, does it not exist? // Computerra, Moscow, 2007. — No. 19 (687) D. Shabanov. On the love of simple explanations // Computerra, Moscow, 2005. — No. 8 (580)