Thursday, January 3, 2013

[Biogeography • 2013] An Update of Wallace's Zoogeographic Regions of the World | including; Saharo-Arabian, Panamanian, Sino-Japanese & Oceanian

Fig. 1. Map of the terrestrial zoogeographic realms and regions of the world. Zoogeographic realms and regions are the product of analytical clustering of phylogenetic turnover of assemblages of species including 21,037 species of amphibians, birds and nonmarine mammals worldwide. Dashed lines delineate the 20 zoogeographic regions identified in this study. Thick lines group these regions into 11 broad-scale realms, which are named. Color differences depict the amount of phylogenetic turnover among realms (for more details on relationships among realms, see dendrogram and NMDS plot in fig. S1). Dotted regions have no species’ records and Antarctica is not included in the analyses. 
Global map shows the division of nature into 11 large biogeographic realms and shows how these areas relate to each other. 

Modern attempts to produce biogeographic maps focus on the distribution of species and are typically drawn without phylogenetic considerations. Here, we generate a global map of zoogeographic regions by combining data on the distributions and phylogenetic relationships of 21,037 species of amphibians, birds, and mammals. We identify 20 distinct zoogeographic regions, which are grouped into 11 larger realms. We document the lack of support for several regions previously defined based on distributional data and show that spatial turnover in the phylogenetic composition of vertebrate assemblages is higher in the Southern than in the Northern Hemisphere. We further show that the integration of phylogenetic information provides valuable insight on historical relationships among regions, permitting the identification of evolutionarily unique regions of the world. [results suggest that the Saharo-Arabian realm is intermediate between the Afrotropical and Sino-Japanese realms, newly define the Panamanian, Sino-Japanese and Oceanian realms]

Wallace's original map published in 1876, denoting six biogeographical realms.

Scientists nearly double the number of biogeographic realms

In 1876, British biologist Alfred Russell Wallace published a map of the world that outlined how related animals were spread over the Earth. For example, Wallace was the first to publicize that North American biodiversity was substantially different from South America, and that an invisible line separated Southeast Asian biodiversity from that of Australia, New Guinea, and nearby islands. With Wallace's research came the founding of biogeography, or the study of species in relation to geography. Today, scientists with the University of Copenhagen have updated Wallace's map—nearly doubling the number of biogeographic realms—with support from data on over 21,000 species.

"Our study is a long overdue update of one of the most fundamental maps in natural sciences," lead author of the new research in Science, Ben Holt, said in a press release. "For the first time since Wallace's attempt we are finally able to provide a broad description of the natural world based on incredibly detailed information for thousands of vertebrate species."

With vast amounts of data, including DNA sequencing, the scientists have created new biogeographic realms, such as the island of Madagascar which is home to lemurs, tenrecs, mini-chameleons, and slew of other bizarre species. Still, much of Wallace's original map survives, such as the split between North and South America, and the line—known as Wallace's Line—separating Southeast Asia and Australia. However, the new study also splits Australia from New Guinea, creating a new biogeographic realm known as Oceania which includes New Guinea and other islands across the Pacific.

"The map provides important baseline information for future ecological and evolutionary research," explains co-lead-author, Jean-Philippe Lessard, at McGill University in Canada. "It also has major conservation significance in light of the on-going biodiversity crisis and global environmental change. Whereas conservation planners have been identifying priority areas based on the uniqueness of species found in a given place, we can now begin to define conservation priorities based on millions of years of evolutionary history."

The map utilizes known data from 6,110 amphibians, 10,074 birds and 4,853 terrestrial mammals.

Well-known as the "father of biogeography," Alfred Russell Wallace was also a consummate explorer and write; spending years in the Malay Archipelago and the Amazon, he wrote extensively on wildlife, ecosystems, and cultures. Wallace even conceived the theory of evolution independent of Charles Darwin, and it was an essay by Wallace on the mechanics of evolution that finally spurred Darwin to write his landmark book, the Origin of Species. 

Ben G. Holt, Jean-Philippe Lessard, Michael K. Borregaard, Susanne A. Fritz, Miguel B. Araújo, Dimitar Dimitrov, Pierre-Henri Fabre, Catherine H. Graham, Gary R. Graves, Knud A. Jønsson, David Nogués-Bravo, Zhiheng Wang, Robert J. Whittaker, Jon Fjeldså, Carsten Rahbek. An Update of Wallace's Zoogeographic Regions of the World. Science. 2012. 10.1126/science.1228282

Scientists nearly double the number of biogeographic realms