Geography Reference
In-Depth Information
Biotas are complex mosaics originated by dispersal and vicariance, having
reticulate histories, which should be studied through different methods.
Evolutionary biogeography integrates distributional, phylogenetic, molecular,
and paleontological data in order to discover biogeographic patterns and as-
sess the historical changes that have shaped them, following a stepwise ap-
proach. In this chapter I briefly introduce the steps of this approach.
One hundred fifty years ago, Charles Darwin published
On the Origin of Spe-
cies
. The geographic distribution of plant and animal taxa was among the
evidence he provided to support evolution. Although the fact that continents
have their own distinctive biotas has been known for some time, from Dar-
win we learned that these biotas evolve, that their composition changes over
time. In the nineteenth and twentieth centuries, biogeographers extensively
debated the mechanisms leading to biotic evolution. In recent years some
authors have concluded that dispersal and vicariance are both relevant pro-
cesses. When climatic and geographic factors are favorable, organisms act-
ively expand their geographic distribution according to their dispersal cap-
abilities, thus acquiring their ancestral distribution (dispersal). When the or-
ganisms have occupied all available space, their distribution may stabilize,
allowing the isolation of populations in different sectors of the area and the
differentiation of new species through the appearance of geographic barriers
(vicariance).
