jueves, 31 de julio de 2008

"Pattern-based" methods

Ronquist and Nylin (1990) introduced the idea of “pattern-based” methods to refer to the plethora of techniques of cladistic biogeography that have as aim finding general patterns of area relationships without taking into account the evolutionary processes that configured those patterns. Except Brooks and his collaborators “pattern advocates” regard as the main point of biogeographic analysis what causes the congruence among taxon-area cladograms and not in what causes ambiguity (Wiley, 1987; Nelson and Platnick, 1981; Ebach, 2001). So, only when a pattern is found the investigator could discuss about the possible vicariant events have took place between the areas. In certain way this is preferable rather than assume that incongruence is due to any other biogeographic event instead vicariance. This cloudy approach is due to a misunderstanding of the relationship between phylogenetic analysis and biogeography, that is if someone wants to introduce transversal transmission needs a method able to test it as a hypothesis (see Sober, 1998). Other methods as paralogy-free-subtree analysis (Nelson & Ladiges, 1996) when remove the paralogy dismissed evidence in order to fix the data into the idea of what biogeographic history behaves. This constitutes a problem in order that it removes other possible vicariant sceneries. Although, any of the denominated “pattern-based” methods allow a clear evaluation of the biogeographical history it is preferable to assume as the only plausible explanation vicariance rather than create sentimental relates based on the incongruence.

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