Biogeographical Classification of the World

Modern biogeographical classification began with De Candolle, Sclater, and Wallace in the nineteenth

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Cladogram

Area of endemism

Figure 1 Steps of a PAE, procedure that allows to identify areas of endemism.

Biogeographical Classification India
Figure 2 Nestedness of the areas of endemism, which is the basis for biogeographical classification.

century. Based on recent studies, Morrone proposed the following biogeographical system for the world:

1. Holarctic realm. It comprises Europe, Asia north of the Himalayan mountains, northern Africa, North America (excluding southern Florida), and Greenland. From a paleogeographic viewpoint, it corresponds to the paleo-continent of Laurasia.

1.1. Nearctic region. It corresponds to the New World, in Canada, most of the USA, and northern Mexico.

1.2. Palearctic region. It corresponds to the Old World, in Eurasia and Africa north of the Sahara.

2. Holotropical realm. Basically the tropical areas of the world, between 30° south latitude and 30° north latitude. The Holotropical region has been previously recognized by Rapoport and would correspond to the eastern portion of the Gondwanaland paleocontinent.

2.1. Neotropical region. Tropical South America, Central America, south-central Mexico, the West Indies, and southern Florida.

2.2. Afrotropical region. Central Africa, the Arabian Peninsula, Madagascar, and the West Indian Ocean islands.

2.3. Oriental region. India, Himalaya, Burma, Malaysia, Indonesia, the Philippines, and the Pacific islands. In spite of the obvious tropical biotic elements of this region, it has been placed in earlier paleogeographic reconstructions as part of Laurasia. Recent authors have postulated that this area was part of Gondwanaland. 2.4. Australian Tropical region. Northwestern Australia.

3. Austral realm. It comprises the southern temperate areas in South America, South Africa, Australasia, and Antarctica. This region has been recognized previously by Kuschel and Rapoport and would correspond to the western portion of the paleocontinent of Gondwanaland.

3.1. Andean region. Southern South America below 30° south latitude, extending through the Andean highlands north of this latitude, to the Puna and North Andean Paramo.

3.2. Antarctic region. Antarctica.

3.3. Cape or Afrotemperate region. South Africa.

3.4. Neoguinean region. New Guinea plus New Caledonia.

3.5. Australian Temperate region. Southeastern Australia.

3.6. Neozelandic region. New Zealand.

Evolution

In order to reconstruct the historical relationships of areas of endemism, Donn Rosen, Gareth Nelson, Norman Platnick, and Ed Wiley developed cladistic or vicariance biogeography. It assumes that the correspondence between taxonomic relationships and area relationships is biogeographically informative. It is based on an analogy between biogeography and systematics, where taxa are treated as characters.

A cladistic biogeographic analysis is comprised of three basic steps (Figure 3):

1. Construction of taxon-area cladograms from taxon cladograms, by replacing the terminal taxa by the area(s) of endemism inhabited where they are found.

2. Conversion of taxon-area cladograms into resolved area cladograms, by resolving problems due to widespread taxa, redundant distributions, and missing areas.

3. Derivation of general area cladogram(s), that represents) the most logical solution for all the taxa analyzed.

Patterns of area relationship derived from a cladistic bio-geographic analysis are interpreted as secondary biogeographical homology. This is the cladistic test of the primary biogeographical homology formerly recognized.

Conservation

Biodiversity is in global crisis. One of the major goals of conservation is the maintenance of as much as possible of the diversity of life. Thus we have to measure and

General Area Cladograms

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South America Australia

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Distribution

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Biogeografical Realems World
Taxon C

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■ North America

I South America Australia General area cladogram

Figure 3 Steps of a cladistic biogeographic analysis, where distributional and phylogenetic data of three different taxa allow to obtain a general area cladogram.

compare priorities regarding areas to be protected, and we need to measure and compare local biodiversity, taking into account not only the number of species, but also the degree of difference among them.

One criterion for measuring biodiversity is species richness, exemplified by the 'megadiversity countries' concept; however, many important components of biodiversity are not represented in countries with highest values of diversity, and some areas could harbor a large number of widespread species, with no great conservation concern. Ecologists have developed diversity measures that combine species richness with information about abundance among species, and information on the vulnerability of those species, including the 'hot spots' analysis. Some authors have suggested that endemicity may help determine priorities for biodiversity conservation,

Areas of endemism (bryophytes) Areas of endemism (gymnosperms)

Lomolino Endemism

Panbiogeographic nodes (bryophytes) Panbiogeographic nodes (gymnosperms)

Pleistocene refugia Hot spots (briophytes and gymnosperms)

Figure 4 Biogeographic analysis of gymnosperms of the world, with the hot spots that resulted from overlap among areas of endemism, panbiogeographic nodes, and Pleistocene refugia. a, Southeastern China; b, Japan; c, New Caledonia; d, Tasmania; e, western North America.

whereas others have argued that it is not an appropriate measure of diversity, and is an ineffective mean for selecting areas for conservation.

A recent analysis of the distributional patterns of bryophyte and gymnosperm taxa of the world has found a remarkable congruence among areas of endemism, panbiogeographic nodes, and refugia in western North America, Japan, southeastern China, Tasmania, and New Caledonia (Figure 4). It was concluded that these areas deserve special status for conservation, being significant candidates for designation as 'hot spots'.

See also: Island Biogeography. Further Reading

Anderson S (1994) Area and endemism. Quarterly Review of Biology 69: 451-471.

Brown JH and Lomolino MV (1998) Biogeography, 2nd edn. Sunderland, MA: Sinauer Associates.

Contreras-Medina R, Morrone JJ, and Luna-Vega I (2001)

Biogeographic methods identify gymnosperm biodiversity hotspots. Naturwissenschaften 88: 427-430.

Contreras-Medina R, Morrone JJ, and Luna Vega I (2003) Uso de herramientas biogeograficas para el reconocimiento de 'hotspots': Un ejemplo de aplicación con briofitas y gimnospermas. In: Morrone JJ and Llorente J (eds.) Una perspectiva latinoamericana de la biogeografía, pp. 155-158. Mexico City: Las Prensas de Ciencias, UNAM.

Cox CB (2001) The biogeographic regions reconsidered. Journal of Biogeography 28: 511-523.

Espinosa Organista D, Aguilar ZUniga C, and Escalante Espinosa T (2001) Endemismo, areas de endemismo y regionalizacion biogeografica. In: Llorente Bousquets J and Morrone JJ (eds.) Introduccion a la biogeografía en Latinoamérica: Teorías, conceptos, metodos y aplicaciones, pp. 31-37. Mexico City: Las Prensas de Ciencias, UNAM.

Harold AS and Mooi RD (1994) Areas of endemism: Definition and recognition criteria. Systematic Biology 43: 261-266.

Morrone JJ (2001) Homology, biogeography and areas of endemism. Diversity and Distributions 7: 297-300.

Morrone JJ (2002) Biogeographic regions under track and cladistic scrutiny. Journal of Biogeography 29: 149-152.

Morrone JJ (2004) Homología biogeografica: Las coordenadas espaciales de la vida. Mexico City: Cuadernos del Instituto de Biología 37, Instituto de Biología, UNAM.

Morrone JJ (2005) Cladistic biogeography: Identity and place. Journal of Biogeography 32: 1281-1284.

Morrone JJ and Carpenter JM (1994) In search of a method for cladistic biogeography: An empirical comparison of component analysis, Brooks parsimony analysis, and three area statements. Cladistics 10(2): 99-153.

Morrone JJ and Crisci J (1995) Historical biogeography: Introduction to methods. Annual Review of Ecology and Systematics 26: 373-401.

Morrone JJ and Escalante T (2002) Parsimony analysis of endemicity (PAE) of Mexican terrestrial mammals at different area units: When size matters. Journal of Biogeography 29: 1095-1104.

Nelson G and Platnick NI (1981) Systematics and biogeography: Cladistics and vicariance. New York: Columbia University Press.

Rosen BR (1988) From fossils to earth history: Applied historical biogeography. In: Myers AA and Giller PS (eds.) Analytical biogeography, pp. 437-481. London: Chapman and Hall.

Wiley EO (1988) Parsimony analysis and vicariance biogeography. Systematic Zoology 37: 271-290.

Williams PH and Humphries CJ (1994) Biodiversity, taxonomic relatedness, and endemism in conservation. In: Forey PL, Humphries CJ, and Vane-Wright RI (eds.) Systematics Association, Special Volume 50: Systematics and Conservation Evaluation, pp. 269-287. Oxford: Clarendon Press.

Zunino M and Zullini A (2003) Biogeografía: La dimensión espacial de la evolución. Mexico City: Fondo de Cultura Económica.

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