Geography Reference
In-Depth Information
law was formulated and tested. As a result of its influence, the idea of a
single center of origin for all species was replaced by the idea of several
“centers of creation,” where creative activity was especially intense. Dar-
win and Wallace explained Buffon's law by chance dispersal, followed in
the twentieth century by Matthew, Simpson, Myers, Darlington, and Mayr.
Some unorthodox authors such as Willis, Rosa, Jeannel, von Ihering, and
Croizat emphasized vicariance as a more appropriate general explanation.
Panbiogeographers and some cladistic biogeographers, such as Nelson,
Platnick, Rosen, Humphries, Parenti, and Ebach, emphasized the idea that
Earth and life evolve together, looking for patterns due to vicariance. Oth-
er cladistic biogeographers, such as Brooks and Lieberman, assumed more
complex scenarios, invoking dispersal in addition to vicariance. The meth-
odological developments of panbiogeography, cladistic biogeography, and
phylogeography illustrate well how evolutionary biogeography has been in-
vigorated by new techniques and approaches, mainly from cladistics and
molecular biology. However, tensions and contradictions continue to exist
because none of the approaches could absorb the others.
The notions of centers of origin and dispersal have been recurrent, al-
though it is debatable whether Linnaeus's Garden of Eden, Darwin and Wal-
lace's centers of origin, and phylogeographers' ancestral areas really rep-
resent the same concept. The notion of vicariance is also recurrent. Is there
necessarily a conflict between dispersal and vicariance? Some believe that
these processes should be considered only after patterns are revealed, tak-
ing a classificatory approach (Ebach and Goujet 2006; Williams 2007b). The
evolutionary approach followed herein is based on the dispersal-vicariance
model that incorporates both processes and fulfills the classificatory object-
ive as a step in the analysis.
Most biogeographers from the twentieth century have considered the
relationships between space, time, and form in one way or another
(Humphries 2004). Panbiogeographers followed Croizat and his
space-time-form sequence, stating that biogeography should be given pre-
cedence over systematics. Dispersalists and cladistic biogeographers used
the sequence form-time-space or form-space-time, giving preeminence to
systematics over biogeography. Evolutionary biogeography, as conceived
herein, follows the sequence space-form-time: The panbiogeographic ana-
lysis (space) constitutes the first step of the analysis, form is incorporated
through the phylogenetic hypotheses used in the cladistic biogeographic
Search WWH ::




Custom Search