Biological Aspects of Endemism in Higher Plants

Rarity of all sorts piques the curiosity of humans. Rare objects, whether discoveries of natural origin or artifacts of cultures, arc avidly sought by collectors and are treasured, housed, and exhibited for the benefit of others. This fascination with that which is rare may partially explain the naturalists' and systematists' time-honored preoccupation with rare and endemic taxa. To be sure, there are sound justifications for acquiring and studying rare organisms. But we suspect that the rarity-seeking syndrome in humans has fostered much of the biologist's preoccupation with rare and endemic plants and animals. The late twentieth century has witnessed exceptional concern for rare organ­ isms and at the same time has seen many rare plants and animals brought close to extinction (22) . The extirpation of rare taxa as well as efforts to preserve rare organisms is the product of the vast human influence on the world's biota. Threatened or endangered taxa have received prime press coverage and, in some instances, legal protection. The Rare and Endangered Species Act of 1973 (US 92nd Congress) and subsequent congressional actions constitute one such response to the threatened loss of the rarer examples of biological divers­ ity. We have no problem, then, in finding a wealth of literature on efforts to conserve rare species. Sources of information on what is rare and on the magnitude of the threat to survival range from the Federal Register's list of