Dispersal hypotheses often associated with arguments about

Dispersal hypotheses often associated with arguments about...

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Dispersal hypotheses often associated with arguments about centers of origin : those regions with the greatest species (or higher rank) diversity. Greater diversity should be due to presence in that region longer (more time for speciation), hence should be the region where the group originated and from which dispersal events took place. Assumes that extant diversity has not moved from origin of diversity. Possible, but not guaranteed for all taxa. Alternative to Centers of Origin and subsequent Dispersal as a way to explain the current distribution of species is vicariance where some barrier to genetic exchange causes the separation of the related taxa. With the acceptance of continental drift, vicariance biogeography became a discipline in which one could test hypotheses (see below). See models in fig. 18.6, 18.8 and 18.9, pgs. 518-521. As with most dichotomies in science: often need to
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Unformatted text preview: invoke Both vicariance and dispersal to account for distributions (not always in the same instance). Example: Galapagos finches had to have dispersed to the archipelago from the mainland and in so doing imposed a vicariance event on themselves. South American land bridge when sea levels dropped in the Pliocene the isthmus of Panama rose and served as an avenue of dispersal for terrestrial mammals (the "Great American Interchange" where unique N.American mammals dispersed to S. America and unique S. Amer. mammals moved north, 3 mil. years ago; see fig. 18.14, tables, 18.2, 18.3, pgs. 528-529), but served as a vicariance event for marine life that was distributed in the region. Lead to the formation of Geminate species (species pairs on either side of the isthmus who are each other's closest relative and were probably one species before the sea level dropped)....
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This note was uploaded on 11/06/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.

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