Biogeography can be a powerful tool to explore data on the diversity, phylogeny, and distribution of organisms, to reveal the biological and geographical history of Earth.<br />
COMPARATIVE BIOGEOGRAPHY<br />Uses the naturally hierarchical phylogenetic relationships of clades to discover the biotic area relationships among local and global biogeographic regions.<br />Approach offers a comprehensive empirical framework for discovering and deciphering of life on Earth.<br />
To introduce comparative biogeography, we differentiate between the two types of biogeographic investigation that it encompasses: systematic biogeography and evolutionary biogeography.<br />
Systematic Biogeography<br />is the study of biotic area relationships and their classification and distribution. <br />For example, the distribution and relationships of numerous taxa may be expressed in a hierarchy as Eastern South America (Africa, India), meaning that organisms in Africa have their closest relatives in India and that together they are in turn related to organisms in eastern South America. Examples include such diverse taxa as vascular plants, fishes, birds, and dinosaurs.<br />
Evolutionary Biogeography<br />is the proposal of evolutionary mechanisms responsible for organismal distributions. <br />Possible mechanisms responsible for the distribution of organisms related as in the area homolog Eastern South America (Africa, India) include widespread taxa disrupted by continental break-up or individual episodes of long distance movement, to name just two.<br />
The idea that the ranges of species was due to their spreading from a point of origination had several precursors before Darwin developed it in 1837<br />
Buffon (father of zoogeography) in 1779<br />Similar species occupy the same position in different ecologies<br />Proposed that a fauna was the product of the conditions of the district where it originated<br />Peter Simon Pallas (German zoologist)<br />Similar forms were often connected by a graded chain of intermediate forms<br />Leopold von Butch<br />Drew the logical conclusion that varieties become segregated species<br />
J G Gmelin (botanist) in 1747<br />First to have suggested that species were independently created all over the world<br />Joseph Hooker<br />Species could spread beyond their allocated domain<br />Charles Darwin<br />Held to be important on islands, but also where rivers, mountains and other impediments prevented species split into separate breeding populations from back-crossing<br />
Mayr<br />Darwin prevaricated on its importance, and eventually also accepted the possibility of “sympatric” speciation – speciation due to a move into new ecological or behavioural niches<br />Alexander von Humboldt (1805), EAW Zimmerman (1778) and CF Willdenow (1798)<br />Species had spread from a central point, the landing site of the Ark<br />Alfred Russel Wallace (1855)<br />Published the principle that species are always found close in space and time to an allied species that precedes it in the geologic record<br />
Wallace did his work in the Amazon region and the Malay Archipelago, while Darwin’s own observations twenty years earlier had been in Galapagos Archipelago and the plains of Patagonia during the Beagle voyage<br />Darwin was spurred into publication of his ideas when Wallace, not knowing of Darwin’s views, sent him a paper on the topic in 1858<br />
Darwin had just suffered the death of his son Charles, and his grief, he passed it on to Lyell and Hooker, with whom he had previously discussed his views who submitted it to the Linnean Society of London with extracts of Darwin’s unpublished 1844 Essay on Natural Selection and a letter wrote to Asa Gray in the United States on 5 September 1857<br />
It is clear that Wallace and Darwin independently discovered biogeography, and are due the joint credit they now are imputed.<br />
Biogeographic Distributions<br />I. Three important principles: How do these principles support descent with modification?<br />A. Environment cannot account for either similarity or dissimilarity, since similar environments can harbor entirely different species groups<br />
B. "Affinity" (=similarity) of groups on the same continent (or sea) is closer than between continents (or seas)<br />C. Geographical barriers usually divide these different groups, and there is a correlation between degree of difference and rate of migration or ability to disperse across the barriers<br />
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