ECOLOGY/EVOLUTION

One if by Land, Two if by Sea

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Science  23 Apr 2004:
Vol. 304, Issue 5670, pp. 493
DOI: 10.1126/science.304.5670.493b

Biogeographers have long debated the relative merits of two competing hypotheses—dispersal and vicariance—to explain similarities in the floras and faunas of widely separated regions such as the Southern Hemisphere landmasses. Similarity by dispersal entails long-distance transport of propagules between landmasses; vicariance entails former terrestrial connections between landmasses, such as those that existed before the continents drifted apart. Phylogenetic methods and increasingly reliable techniques for paleogeographic reconstruction are helping to resolve the relative importance of the two processes. Sanmartín and Ronquist find a distinction between the biogeographic histories of Southern Hemisphere plants and animals. Animal distributions and phylogenies largely match the sequence of the breakup of the Gondwana landmass that produced the modern continents, with evidence for limited dispersal between Australia and South America. In contrast, the plant data indicate a dominant role for dispersal. — AMS

Syst. Biol. 53, 216 (2004).

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