Dry Store Room No. 1: The Secret Life of the Natural History Museum. Richard Fortey

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СКАЧАТЬ pass their lives without seeing a truffle of any kind, and who but an outstanding eccentric would spend hours carefully digging around in the litter under trees to find false truffles of the inedible kind? But then, who would guess that truffle evolution was crucial to the survival of several charming Australian marsupials? For the Australian group of truffles, including some placed in the genus Hydnangium, were also independently evolved in close association with Eucalyptus trees. These false truffles provide a prime foodstuff for bettongs and potoroos, which are delightful, nocturnal cat-sized animals that are now the focus of intensive conservation efforts. The more that is known of their requirements the more likely they are to survive in the twenty-first century. False truffles are as important to their continued existence as keeping them from the depredations of feral cats. So what might at first seem extraordinarily specialized information has links to those ‘pretty furry things’ after all; nature is seamless, its connections multifarious.

      The truffle example also links back to where we started – the questions of taxonomy. Every time a truffle under examination turns out to be related to an entirely different mushroom, we can imagine a curator cursing quietly under his breath and moving the relevant preserved specimens to a different drawer. This is an extreme case of ‘revision’ – revisiting taxonomy. The point is that we expect classification systems, genera, families and so on in ascending order, to reflect fundamental resemblances between the species included in them. The species themselves are the units of this classification – at least they are if we have recognized them correctly – and they are the real things that get shifted around from one drawer to another. The genus or family whose name might be written on the drawer or cupboard is a theoretical concept, subject to change as science advances. As with the truffles, species may be added or taken away or moved around. The up-to-date taxonomist wants his classification concepts to square with modern views. For most such scientists this means that the species included in a genus, for example, should have descended from a common ancestor – that is, constitute what is known as a clade. The characters shared by the species in a genus – and nowadays these can be molecular characters as much as the traditional ‘hairs on legs’ – are what defines it, makes it a natural entity. Discover new characters and the concept of the genus may well change, and so will the species included within it. This results in changes in generic names for a given species that irritate many people, and particularly knowledgeable amateur scientists. ‘Why do they have to keep changing the names?’ is a common complaint. However, the contemporary investigator is obliged to seek out genera, or families, that are clades; the scientific method used in recognizing these groups is known as cladistics; and the whole business of examining relationships between organisms in this way is usually termed phylogenetic analysis, or simply phylogenetics. If names have to change as a result of careful reconsideration of species, well, that’s the price of progress. Much modern taxonomy is based upon computer analysis of relationships, where all the characters possessed by a group of organisms under study are allowed to fight it out until the ‘best’ arrangement of species is discovered, resulting in a diagram – a cladogram – showing how species relate to one another. The eventual classification is then drawn up directly from the cladogram. For example, several clades of species clustering together might be recognized as separate genera, and if these genera then cluster together in a more inclusive group this larger group might be the basis of a family.

      This sounds technical, and so it is. Quite a few famous taxonomists are computer experts first, and lovers of organisms second. They think in algorithms rather than algae. They are mostly interested in animals and plants as experimental material for their classificatory computer programs. Their conversation tends to revolve around the statistical criteria for the support of one piece of the cladogram or another; an outsider hearing these people chatting might think she was overhearing an unknown Amazonian language. However, arcane though it might sound, the cladistic approach has made taxonomy much more of a science, and less dependent on the word of an authority alone. It provides a unifying method across the spectrum of organisms, from virus to vicuña, and can embrace all kinds of evidence, from the molecular to the anatomy of a blue whale. But it will be clear by now that it also makes problems for that Linnaean system of naming animals and plants. Linnaeus himself designed his ‘system of nature’ before the notion of evolution had gained currency. Some might have considered that the order of nature might be an expression of the mind of God alone: ‘he made them high and lowly, he ordered their estate’, as the hymn puts it. The idea that classification might involve notions of descent from a common ancestor was a subsequent introduction. The species as the unit of currency of classification was the only thing in common between these pre- and post-Darwinian worlds. And with the arrival of cladistics and molecular analysis the old Linnaean system might be seen to creak and groan under the stress of frequent changes in nomenclature – so much so that some scientists have tried to persuade their colleagues that the time has come to abandon the Linnaean binomial altogether. They want to replace it, or at least augment it, with something called the PhyloCode.

      As this is written the PhyloCode is still undergoing its own evolution, and it might be premature to anticipate the outcome. Many critiques of the Linnaean system are surely correct. There is no consistency in the use of the ranks of the system between different kinds of organism; some parts of the natural world have small genera, other parts have large ones, and a family can be a very different concept from one worker to another. We already have an intuitive feel for this. Birds are finely divided into genera separated by tiny anatomical differences; on the other hand some genera of plants and fungi might include several hundred species. The attractive sea snail genus Conus includes at least six hundred species. The recognition of what makes a genus or family is partly a matter of tradition and taste. It is also undoubtedly true that there are not enough categories to recognize all the different levels of relatedness that a modern cladistic ‘phylogenetic tree’ can recognize, and nobody wants extra formal ranks with names like supersubfamilies or subsuperfamilies. There are quite enough names already.

      PhyloCode is based entirely on cladistic phylogenies, and provides a system for naming clades – all of them. The old formal Linnaean categories above species level are abandoned. This is a rather revolutionary suggestion, to say the least, and it is not surprising that it has excited some strong opposition. To my mind the strict logic of the PhyloCode is beside the point. The most important thing about the current system of naming organisms is the common language it provides, not just to other systematists, but to the rest of the world – people like gardeners, or bird watchers, or fungus forayers. Very few members of this larger community know about the details of cladistic phylogenetic analysis, and I suspect that most of them want a meaningful label that they understand rather than reassurance that every category is quite the latest collection of good clades. The 250-year tradition since the great Swedish systematist does count for something. Many of the common categories that a naturalist will comfortably recognize are old Linnaean families. Think of lilies (Family Lilaceae) or daisies (Family Asteraceae) or crows (Family Corvidae). These turn out to be pretty good clades as well, meaning that the resemblance between the species in the families does indeed reflect descent from a common ancestor. In my experience more ‘difficult’ groups of organisms are often reanalysed time and again using the latest cladistic bells and whistles or new molecular evidence, and each new analysis is rather different from the last one. Nor is there any guarantee that the latest version is always the best. Potentially all these different analyses could be named under PhyloCode. In my view this would allow for just too many valid names, as each successive analyst sought to put his imprimatur on his briefly dominant hierarchy. But most important of all is a feeling that offends my democratic instincts, in that the systematization of nature would be even more in the hands of a coterie of specialists sitting in front of their computers than it is now. The binomial system has faults, but I suspect any new system would develop as many. The naming process would be taken away from the naturalists, nature lovers and intelligent laymen, at a time when there has never been so much pressure on the survival of species, or, indeed, on the survival of the taxonomists who know about fleas and carabids, trilobites and ammonites, grasses and orchids, or deep-sea worms. It is the survival of the biological world and of the basis of expertise that studies it that is the real concern of the twenty-first century. Names are the least of it.

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