It was supposed to be an upbeat meeting. This was an international gathering of plant scientists at a con­gress that takes place once every six years. And the setting was perfect too. The Missouri Botanical Gardens in St. Louis, is a world class facility. Not only are the gardens themselves wonderful, but a large group of research scientists conduct their studies on site. The con­gress attendees, in early August 1999, were prepared to hear the results of a five-year study on plant classification. The project, designed as the botanists' answer to the human genome project, had involved 200 scientists from 12 countries. "Deep Green" was the fanci­ful code name for this study based on DNA sequences (chemical details of ge­netic information). Most conferences generate some disagreements between various participants, but this one seemed downright acrimonious. Could those be angry voices heard in the after­math of the conference?

The problem was that the patterns of DNA information were not what had been expected. It had been anticipated that plants, which looked alike, would also exhibit similar details in genetic information, but this was not always found. As a result, some of the more rad­ical scientists at the conference recom­mended that plant classification should be drastically overhauled. Plants which appear similar (in such characteristics as flower parts) might now be relocated into alternative groups with quite different plants. The result would be new scientific names for many plants and a classifica­tion scheme that would be understand­able only in terms of extremely high tech biochemical studies of DNA. Horticul­turists and people who routinely work with living plants, were aghast at the prospect. They retorted that they would not accept any such new schemes.

Father of Botany⤒🔗

Plant classification has had a long history. It was Theophrastus (370-285 BC) who first categorized plants into groupings with similar characteristics. In his case the criterion for assignment to one or other group was on the basis of growth form such as trees, shrubs and herbs. For this contribution, Theophras­tus is recognized as the Father of Botany. This was not however a discipline which rapidly developed after its first begin­nings. Further progress had to wait al­most two thousand years! Swiss botanist Joseph Pitton de Tournefort (1656-1708) observed that certain trees, while obvi­ously of the same basic design, neverthe­less were consistently different in detail. Thus this man is recognized as father of the concept of genus. In biology, a genus (plural genera) represents a group of closely similar designs. The observed variations on the genus theme (for ex­ample maple trees as opposed to oak trees) are designated as species. A species is considered to be the smallest group of individuals that can be consis­tently recognized as a group. For exam­ple, sugar maples can be consistently be distinguished from red maples and Man­itoba maples. It was Toumefort's contri­bution to recognize that groups of plant species could be clustered into genera based on their characteristics. The stage was now set for Carolus Linnaeus (1707­-1778), of Sweden.

Linnaeus loved plants. Although he was trained as a medical doctor, he even­tually became professor of botany at the University of Uppsala. In his efforts to or­ganize plants, he used a single Latin word to designate each species in a genus rather than the cumbersome descriptive Latin phrases then in use. For example, sugar maple became Acer saccharum and red maple Acer rubrum. Moreover in his book Species Plantarum, published in 1753, he also grouped all the plants into one or other of 24 classes. These classes were established for convenience of identifi­cation. Linnaeus believed in separate creations of species and so did the botanists who followed him for more than a century. Some people today believe that the reason organisms can be catego­rized is because they have all developed as a result of an evolutionary process. This however is an erroneous impression. Our ability to classify merely reflects the fact that organisms contain information. Anything that can be described, can be categorized. The early taxonomists viewed organisms as products of design, the handiwork of God.

Refinements Continue←⤒🔗

The process of refining the classifica­tion system continued. Another eighteenth century botanist, Antoine Laurent de Jussieu, was the first to group plants into families of genera with roughly similar characteristics. Many of his groupings cor­respond closely to families recognized to­day. Modern taxonomists indeed recognize that evolution theory was not needed to develop our current approach to plant tax­onomy (classification). As one specialist re­marked a few years ago, "It is certainly true that highly predictive classifications can be constructed without any knowledge of population dynamics or phylogeny (as was done effectively from 1759-1859; note par­ticularly the early system of Jussieu, 1789)..." (T. F. Stuessy. 1979. American Zoologist 19 p. 623).

Evolutionary Attempts←⤒🔗

Thus in its basic outlines, plant tax­onomy or classification was established as a logical system with only very weak connections to evolution theory. Never­theless, botanists since Darwin have tweaked the system this way and that, in an effort to produce a classification sys­tem which reflects lines of evolutionary descent. Their approach can be likened to someone dealing with a human pop­ulation. Siblings share an immediate ancestral pair, their parents — so they would be grouped together. The common ancestor of first cousins is a further gener­ation back — so they are placed in a larger category that includes various sibling clusters, all first cousins. Second cousins are connected yet a further generation back, so they are placed in yet a larger category that includes various first cousin clusters. In similar fashion, biolo­gists try to cluster plant families together in such a way as to reflect evolutionary relationships. There is however a major problem in such studies. These are very subjective assessments. Specialists seldom agree on how to group the plants. The situation in fact seems nothing short of chaotic. One scientist surveyed the views of various plant taxonomists and he reported: "There is no general agree­ment on the delimitation of vascular plants (most of the land plants) into di­visions; in the eighteen books examined, seven authors recognize a single divi­sion, the Tracheophyta, but the remain­der split them into seven to eleven divisions" (P. Edwards. 1976. Taxon 25 #5/6 p. 537). The difference in conclu­sions among these experts came from disagreements over the course of events in plant evolution. Meanwhile quite a different approach to taxonomy was be­coming popular.

Plenty of controversy surrounded the appearance of a classification technique that made extensive use of com­puters. In order to carry out this scheme, the classifier could forget about specific evolutionary scenarios. All he needed was a mathematical equation (algorithm) and a data bank on the organ­isms under study. The computer then lumped the organisms into two groups based on their possession or lack thereof, of one trait or characteristic. Thus the two groups could be called the "haves" and "have-nots" for one characteristic. This process would then continue with each group successively split into two groups. The resulting chart looked like an evolutionary tree (lines of descent) but it was produced in quite a different fashion. Dubbed cladistics, this classifi­cation scheme was vigorously fought by many traditional evolutionists. After all, it is possible to categorize anything and the graphs thus developed, did not nec­essarily reflect any biological relation­ships at all. However cladistics has one feature in its favor. It is the only way to handle large banks of data. Thus the new proposed Deep Green classifications are not only cladistic, but also entirely different from current schemes.

Faulty Assumptions←⤒🔗

In the past, scientists have assumed that organisms that are alike are in fact related by descent. Somewhere in the past, they came from the same popula­tion. One would expect therefore that their genetic information would be simi­lar too. But this is not what the Deep Green scientists found. In many cases, they found that plant groups which should be closely related by descent, in fact exhibited quite different genetic in­formation. There are two possible expla­nations for this. One is that the various groups of organisms were separately cre­ated, so that the genetic information would not necessarily be similar. As long as it works, that is what matters in de­signed systems. Alternatively, if the DNA sequences do in fact indicate lines of de­scent, then similarity in appearance has little to do with evolutionary relation­ships. Faced with such choices, the Deep Green scientists concluded that evolution has produced similar plants through sev­eral lines of descent. This would be quite a coincidence if there were many in­stances like this. The greater the number of such instances, the more unexpected such conclusions are. Nevertheless, most botanists support this explanation since the alternative, which is separate cre­ations, does not appeal to them.

Some influential botanists, however, caution against a hasty revamping of plant classification. Each cladistic plot is based on a mathematical equation or al­gorithm. There are many such equations to choose from and each produces dif­ferent results. Moreover the calculations are also drastically influenced by the se­lection of data. Different choices often yield different groupings. Observers may well conclude that the situation is highly uncertain and unstable. At the present time, these seem to be reasonable con­clusions. DNA sequence studies involv­ing other groups of organisms similarly seem to be leading to devastating up­heavals in traditional classifications. If the organisms were separately designed, this is to be expected.

At some point, scientists will have to decide whether they want classifica­tions that are practical to use, or ones that reflect constantly changing views on evolutionary relationships. Don't hold your breath that common sense will prevail.