Beyond Cladistics: The Branching of a Paradigm

4. Do We Need to Describe, Name, and Classify All Species?

67 FOUR Quentin D. Wheeler DO WE NEED TO DESCRIBE, NAME, AND CLASSIFY ALL SPECIES? All science is either physics or stamp collecting. Ernest Rutherford Rutherford was more candid about his bias than most experimental biologists are in sharing their view of taxonomy (see quotation). To the outsider, taxonomy may look a bit like philately. We do want to collect every species, but the similarity stops there. Our motive is to explore unique characters and all their subsequent modifications through evolutionary history (Platnick 1979), to determine what they mean in terms of species, relative recency of common ancestry among species, and as the basis for informative and predictive classifications. This is achieved through painstaking comparative studies and analyses of patterns of distributions of characters and through the creation and critical testing of hypotheses on many levels, from homologues to synapomorphies, clades, and geographic distributions. These hypotheses are almost invariably more rigorous than experiments . The fact that the outcome of most experiments can be any of a universe of possible outcomes means that we must resort to statistics to determine whether our results are significant. For the vast majority of Beyond Cladistics: The Branching of a Paradigm, edited by David M. Williams and Sandra Knapp.Copyright byTheRegentsoftheUniversityofCalifornia.Allrightsofreproduction in any form reserved. 68 / ON CHRI S hypotheses in taxonomy, the predicted outcomes are precise and clear. In the frame of reference described by Karl Popper (1959), taxonomic hypotheses are all-or-nothing claims about the world. No claims are more vulnerable to refutation than such statements. All insects have six legs. All Rosaceae have flowers with five petals. All populations of this species share a specified and unique combination of characters. All species of that clade share the following synapomorphies. All species of Nothofagus occur in the Southern hemisphere. In each case, our observations of hundreds or thousands of specimens have revealed a pattern that we now generalize as an all-or-nothing prediction. As new specimens are seen and characters newly discovered, each is an opportunity to test the prediction. These tests are so severe that a single observation can refute the hypothesis (Gaffney 1979). One eight-legged butterfly, one leech with a vertebral column, one Nothofagus in Canada, and no statistical test is needed to reject the hypothesis. Ecosystem scientists can measure the capacity of frozen tundra as a carbon sink without knowing or caring what species of mosses or lichens are growing on the rocks or what species of microbes are living in the soil. Many laboratory experimentalists need to minimize variations and so focus on one or a few model organisms and feel no need for the ability to identify species in the field, even those closely related to the model species. Conservation biologists and land managers overseeing a large national park are winning and losing battles to stave off poachers and keep development at bay around the perimeter of the park and do not see a great need to have a complete inventory of the species in the park to succeed at either. Agriculturalists primarily work with a handful of crop species and a known and limited set of primary pest species for each of those crops and thus may have a narrow interest in biodiversity. Convincing the world of the fact of evolution in the latter half of the nineteenth century was a beginning, not an end. From that beginning we set out to unravel the mysteries of inheritance, gene expression, and selection right down to the molecular level. Similarly, we have begun to reconstruct the origin and diversification of species and characters that are the evidence for understanding evolutionary history. For centuries no one questioned the importance of taxonomy. It was as self-evidently important to explore the world’s species as it was to map its continents and ocean floors, chart the stars of the Milky Way, or probe the structure of atoms. Somehow, simply knowing that evolution DO W E NEED T O DESCRI BE, NAME, CLASSIFY? / 69 was responsible for species massively shifted funds and attention to mechanisms of microevolution and away from studying the results of evolution itself. This is bizarre. Believing that the Universe arose from the Big Bang did not deter exploration of galaxies; knowing there were seven continents did not retard our exploration of the four corners of those landmasses; and realizing that atoms are comprised of particles did not discourage physicists from continuing to...