Biogeography - Группа авторов

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new adaptations. Populations would form faunal elements, thereby relinquishing the need for formal areas. You can have Old World elements in the New World, populations that disperse and establish themselves as new populations in new areas. Populations could also form refuges in cases of changes in climate or landscape, such as advancing ice caps. At the population level, so many more current geographic and climatic events can be used to explain the distribution of populations. Yet, the area classification remained; only the way plant and animal geographers define their areas varied. Mayr, who thought the Sclater–Wallacean areas were static, “descriptive, essentially regional, and non-dynamic” (Mayr 1946, p. 4), proposed a “Classification of faunal elements of the Americas” (Mayr 1946, p. 11), in which the elements were defined as “Old World”, “Holarctic” and “Pantropical”. These are the same static areas Mayr denounced earlier in the same paper. The only difference is that the subregions are treated as “faunal elements”, that is, populations, which are assumed to have dispersed between the larger regions.

      Plant communities, populations or faunal elements are simply ways in which we describe the smallest unit of classification. We may speak of a population of koalas, but koalas (Phascolarctos cinereus) have to be identified through a unique or diagnostic set of characteristics. Koalas are diprotodontids and share the characteristics of other diprotodontids, such as kangaroos. Kangaroos and koalas are marsupials, such as the American opossum, and kangaroos, koalas and opossums are mammals. Without such a classification, we would not be able to identify a population or various individuals within a community. The “two courses”, namely vegetation and species (flora) classifications, which were so prevalent in plant geography and classification during the early 20th century, did unify by the 1940s. In 1947, Ronald Good proposed a “classification of the world into floristic units” (Good 1965, pp. 30–32), which was updated by Takhtajan et al. (1986). The hierarchical classification, divided up into kingdoms, subkingdoms and regions and subregions, is reminiscent of the Sclater–Wallacean regions (i.e. Neotropical, Indo-Malaysian, Australian). The smaller subregions are based on climate (e.g. Central Deserts) or geopolitical or geographical areas (e.g. Borneo, Mexican Highlands) and seem to resemble plant communities. Good seems to have combined the larger regions with the smaller plant communities into a single classification. In zoogeography, the Scalterian–Wallacean regions prevailed into the 21st century. Early objections to a “static” area classification never challenged how the classification functions, but rather how areas are defined. Ortmann (1902) was very particular on how areas should be defined:

      1) Any division of the earth’s surface into zoogeographical regions which starts exclusively from the present distribution of animals, without considering its origin, must be unsatisfactory, since always only certain cases can be taken in while others remain outside of this scheme.

      2) Considering the geological development of the distribution of animals, we must pronounce it impossible to create any scheme whatever that covers all cases.

      3) Under these circumstances it is incorrect to regard the creation of a scheme of animal distribution as an important feature or purpose of zoogeographical research (Ortmann 1902, pp. 269–270).

      The Sclater–Wallacean areas are still in use today, and various authors using geospatial methods have identified similar classifications to that of Sclater and Wallace (Figure 1.6) using different models (Kreft and Jetz 2010; Proches and Ramdhani 2012; Holt et al. 2013; Figures 1.7–1.9). If we look at these three different studies using different data, methods and theories, we find that the same Sclaterian–Wallacean areas keep appearing. While these approaches have different origins in their ideas and methods, the practice of looking at and proposing area classification has not changed since (Zimmermann 1777).

Schematic illustration of a map showing the Zoo-Geographical Regions and the contour of the Ocean-bed.

      Figure 1.6. “Map of the World, showing the Zoo-Geographical Regions and the contour of the Ocean-bed” (Wallace 1876, frontispiece). For a color version of this figure, see www.iste.co.uk/guilbert/biogeography.zip

      Let’s return to Goethe’s observation that “the history of science is science itself”. In the case of area classification, we see that biogeographers keep doing the same thing, proposing area classifications, but using very different and independent approaches. If we look at scientific theories and methodologies, we find multiple origins in biogeography. But biogeographic practice, namely area classification, seems to constantly reinvent itself. The history of science is truly science itself.

Schematic illustration of a map showing the six major biogeographical divisions. Schematic illustration of a map showing vertebrate zoogeographical regions and subregions.

      Figure 1.8. Vertebrate zoogeographical regions and subregions (Proches and Ramdhani 2012, Figure 1.2). For a color version of this figure, see www.iste.co.uk/guilbert/biogeography.zip

Schematic illustration of a map of the terrestrial zoogeographic realms and regions of the world.

      1.4. Conclusion

      It is impossible to practice biogeography without an area classification, whether those areas are simply geopolitical, geographical or based on endemism or taxonomic distribution. The plant and animal geographies of the 18th, 19th and early 20th centuries have shown us that no matter how you divide up the world, you have to call your areas something. How plant and animal biogeographers define their areas also depends on the background of the authors. Humboldt, a naturalist, wished to use plant form and vegetation; de Candolle, a taxonomist (in fact, he coined the term taxonomy), used the distributions of species in what was later described as topographical plant geography; Schouw, following in the Humboldtian tradition, used vegetation; Alphonse de Candolle, a systematist, preferred to use endemism; Mayr, an evolutionary biologist, wanted to use populations or elements. Regardless, they were all doing the same thing, area classification, in order to express their theories of the world using a variety of different methods. Yet, area classification seemingly had its detractors, namely those who thought it was static or artificial. These objections were mostly about how areas are defined, rather than area classification per se. Area classification will always be practiced as long as there is a study of the distribution of organisms.

      1.5. References

      Brundin, L. (1966). Transantarctic relationship and their significance, as evidenced by chironomid midges. With a monograph of the subfamilies Podonominae and Aphroteniinae and the austral Heptagyiae. Kungliga Svenska Vetenskapsakademiens Handlingar, 11, 1–472.

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