DEVORE, MELANIE L. Department of Biological and Environmental Biology, Georgia College and State University, Milledgeville, GA 31061. - Tectonism and its impact on the biogeography of South America.
Biogeographical patterns observed in floras are the result of a number
of historical factors. Biogeographers have viewed tectonic events as
significant historical factors influencing patterns of species
richness, endemism, and biotic history based on phylogenetic analyses.
In many cases, biogeographers consider tectonic events in the context
of major plate movements resulting in continental separation,
convergence and generalized orogenic events. Other phenomena
associated with major plate movements, as well as motions of smaller
"microplates", have also had a considerable impact on the
evolution of major groups and development of biota. In particular,
plant evolution and floras of South America have been strongly
influenced by tectonic events on several scales. Microplate movements
have played a significant role in the continental evolution of both
the northern and southern margins of the continent. Hot spots and
their associated aseismic ridges have also influenced the development
of floras on both the eastern and western margins of South America.
Finally, recent studies have indicated that the main Andean
deformation consisted of a series of events starting in the Jurassic
(Andes of Columbia-Ecuador) and continuing into the present. These
events have resulted in segmenting the 9000 km mountain range into
seven sections. Each section has a distinct orogenic history of its
own. The potential impact of these events on biota was examined using
both distribution data and phylogenies of selected angiosperm groups.
Although we think of the evolution of older groups being influenced by
tectonics, younger families (e.g. Asteraceae and Calyceraceae) also
have histories tied with tectonic events.
Key words: Biogeography, Phytogeography, South America, Tectonics