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Animal geography had a later start than plant geography. Although Zimmermann (1778–1783) was the first to consider an animal geography, it was confined to quadrupeds. Unlike the Humboldtians and de Candolle, animal geographers rarely looked at faunal regions, instead preferring to look at taxon-specific distributions. Also, a contemporary of Zimmermann, Johan Christian Fabricius, proposed eight climatic regions “from which the Stations of insects are judged” (Fabricius 1778, p. 154). Zoologists did not adopt the Humboldtian tradition of using “form” and dismissed the climatic regions of Fabricius as arbitrary or artificial:

This simple statement is enough to convince us that there is a lot of arbitrariness in these divisions (Latreille 1815, pp. 40–41, my translation).

[Fabricius] … by not attempting to demonstrate the correctness of any one of his divisions, seems to have subsequently abandoned them altogether, since no one, it may be fairly presumed, was more qualified than himself to discover the artificial nature of his theory (Swainson 1835, pp. 10–11).

Similarly, the regions proposed by Pierre André Latreille in 1817, based on latitudinal and longitudinal gradients along climatic zones, were equally dismissed:

Any division of the globe into climates, by means of equivalent parallels and meridians, wears the appearance of an artificial and arbitrary system, rather than to one according to nature (Kirby and Spence 1828, p. 487).

Entomologists William Swainson, William Kirby and William Spence were insistent on the necessity of defining natural regions, namely “those grand divisions of animal geography pointed out by nature, and immediately recognized by every naturalist” (Swainson 1835, p. 11). Swainson places William Sharp Macleay and Humboldt among those who recognize that natural areas are not “regulated by isothermal lines” (Swainson 1835, p. 12). The famous Tableau Physique of Humboldt, depicting mounts Chimborazo and Cotopaxi in the Andes, were drawn in cross-section in order to highlight isothermal lines⁴ (Figure 1.4). We can imagine that Swainson considered all lines, be they isothermal lines or latitudinal lines, as artificial. Yet, isothermal lines were quite popular with plant and animal geographers in delimiting climatic zones. Given, however, that climate and plant forms define vegetation, we could argue that the Humboldtians would consider such lines to portray natural areas. After all “only those vegetative formations deserve to be recognised as independent plant forms, which conform to the influence of climate” (Grisebach 1866, p. 384).

Figure 1.4. Humboldt’s Tableau physique showing a cross-section of Mount Chimborazo and Mount Cotopaxi in the Andes. The full title of the map reads: Geographie des plantes equinoxiales : tableau physique des Andes et Pays voisins. Dressé d’après des observations et des Mesures prises sur les lieux depuis le 10.degré de l’attitude australe en 1799, 1800, 1801, 1802 et 1803 (in Humboldt and Bonpland 1807) (source: http://cybergeo.revues.org/docannexe/image/25478/img-7.jpg). For a color version of this figure, see www.iste.co.uk/guilbert/biogeography.zip

While some zoologists would adopt a more Humboldtian approach to delimiting areas using climate, such as the homoiozoic belts of Forbes (1856) or the life zones of Merrian (1892), others sought to look only at the distribution of species. An earlier attempt at using animal distributions to define animal regions was proposed by Johann Karl Wilhelm Illiger in 1815. Illiger (1815) attempted to summarize the global geographical distribution of mammals by counting the number of species that occurred in each continent. Much of Illiger (1815) are tables listing the names of genera, families and orders and the numbers of species found in each continent. The work is completely taxonomic, devoid of any measurements of temperature or rainfall, and synthetic, as it had collated names of species from the works of others. The body of work is divided into sections or “comparative summaries” based on each of the tables, including a description of the faunal distribution of a list of the taxa. A modern-day biogeographer would be impressed with the volume of data but perplexed with how little Illiger had done with it. German paleontologist Johann Andreas Wagner synthesized Illiger (1815) into four mammalian provinces in a three-part work published between 1844 and 1846 (Wagner 1844–1846). The work also included the first known global biogeographic map (Figure 1.5). Wagner was also the first to use a hierarchical classification of zones, provinces, sub-provinces and regions (Table 1.1). More important, Wagner considered these divisions to be natural. In staying with Illiger’s style of only listing the distributions of mammals, Wagner stands out in zoological and botanical geography by ignoring abiotic factors such as climate. Wagner’s contemporary Ludwig Schmarda’s Distribution of Animals (Schmarda 1853), for example, discusses the influence of climate, water and temperature, as well as denoting “tropical forms” and the interaction with vegetation. Schmarda’s map of the geographical distribution of animals is possibly the most detailed of any zoogeographical study in the 19th century. The map depicts 21 terrestrial and 10 oceanic areas and the distributions of various taxa, as well as the location of reefs, atolls, the direction of ocean currents, isothermal lines and latitude and longitude. Unlike Wagner’s classification, Schmarda’s was non-hierarchical and partially based on climate. Unfortunately, Wagner’s work was largely ignored and those who did notice it never quite fully appreciated its significance. The nearest zoogeographical work to resemble Wagner’s appeared a decade later. Philip Lutley Sclater, who used a similar method to Wagner, namely counting taxa, proposed a hierarchical classification. Sclater, however, offered something new:

In the Physical Atlases lately published, which have deservedly attracted no small share of attention on the part of the public, too little regard appears to have been paid to the fact that the divisions of the earth’s surface usually employed are not always those which we most natural when their respective Faunæ and Flora are taken into consideration. The world is mapped out into so many portions, according to latitude and longitude, and an attempt is made to give the principal distinguishing characteristics of the Fauna and Flora of each of these divisions; but little or no attention is given to the fact that two or more of these geographical divisions may have much closer relations to each other than to any third, and, due regard being paid to the general aspect of their Zoology and Botany, only form one natural province or kingdom (as it may perhaps be termed), equivalent in value to that third (Sclater 1858, pp. 130–131).

Figure 1.5. “Representation of the distribution of mammals according to their zones and their provinces. The southern boundary of the northern polar province is indicated by a line of a different color, drawn somewhat further south than the equatorial border of the arctic fox ([Vulpes] lagopus), though not so far in some places as the reindeer may descend there on their summer migrations. The southern polar province is not included in this map, because it is only in the process of discovery and, according to all previous experience, it does not harbour land mammals” (Wagner 1844, 241, Table 1.1). For a color version of this figure, see www.iste.co.uk/guilbert/biogeography.zip

Table 1.1. The hierarchical classification of zones, provinces, sub-provinces and regions listed in Wagner (1844–1846). Note that Wagner considered a third Southern Polar province, but omitted it partly because “we know too little about it and partly since it has no land-animals, and the marine mammals for the most part the same ones are found on the coasts of South America, South Africa, and Australia” (Wagner 1844, p. 86)

Zone	Province	Sub-Province	Region
Northern	Polar	Europe
		Nowaja Semlja
		Siberia
		America
		Greenland
	Old World	a. Middle Europa
		b. South Siberia
		c. Binnenmeerisches Steppes
		d. Mediterranean Basin
		e. High Asia
		f. Japan
	North America	Temperate North America
Middle or	South Asia	–
Tropical
	Africa	South Africa
		West Africa
		Madagascar
	Tropical America	I. Western Slopes	a) Coastal region
			b) Western Sierra region
			c) Cordilleran region
		II. Eastern Slopes	d) Pana region
			e) Eastern Sierra region
			f) Forest region
Southern	Australian	Southeast Australia
		South Australia
		Southwest Australia
		Northwest and North
		Australia
		Van Diemansland
	Magellanian	Pamas
		Patagonian
		Chilean
	Southern Polar	–

Sclater mentions the relationships of natural areas, a concept that was to appear over a century later (see Hennig 1950, 1966; Brundin 1966), but was never explored further in his 1858 essay. Sclater’s regions were adopted by Wallace (1876), who shared similar sentiments regarding arbitrary lines:

The divisions in use till quite recently were of two kinds; either those ready made by geographers, more especially the quarters or continents of the globe; or those determined by climate and marked out by certain parallels of latitude of by isothermal lines. Either of these methods was better than none at all; [but] it will be evident, that such divisions must have often been very unnatural, and have disguised many of the most important and interesting phenomena which a study of the distribution of animals presents to us … The merit of initiating a more natural system, that of determining zoological regions, not by any arbitrary or a priori consideration but by studying the actual ranges of the more important groups of animals, is due to Mr. Sclater (Wallace 1876, vol. 1, pp. 52–53).

Wallace’s revision of Sclater’s regions is perhaps the most significant of all the geographical classification of the 19th century as it unified zoogeography under a single classification. Even though there were certain disagreements over terminology (see Ebach 2015), the areas have withstood the test of time, with the same divisions appearing in the 21st century studies (e.g. Holt et al. 2013; Morrone 2015). Regardless of its popularity today, the Sclater–Wallacean areas and the whole notion of topographical zoogeography were challenged as “essentially static” and “wrong”. “Instead of thinking of fixed regions, it is necessary to think of fluid faunas” (Mayr 1946, p. 5). For the newly developing field of population genetics and the Modern Synthesis, “zoogeography has had a similar fate very much like taxonomy. It was flourishing during the descriptive period of biological sciences. Its prestige, however, declined rapidly” (Mayr 1944, p. 1). Taxonomy apparently had run its course. Long live populations!