Biogeography

The Application of Modern Technology

   G.F. Guala


Geographic Information Systems (GIS).

With all of the data being generated, new ways are needed to store, manipulate and analyse it.  Geographic Information Systems are the answer.  They can be of two types: raster or vector. Raster systems like the one below are best for analyses because you can run any statistic on, or through, them that you can run on a flat array or spreadsheet.  Vector systems use polygons to store data and are very efficient in terms of space and CPU power when large areas have a single value.  Essentially, in a vector system, the computer generates a mathmatical description of the boundary of a polygon and ascribes a certain attribute (the content) to the entire area bounded by that polygon.

The GIS is a computerized geo-referenced database that is specifically designed for spatial data.  Shown is a raster, or pixel, based system.  Simply put, it  works like an enormous database with each data-layer (e.g. soils or rainfall) being a record with several thousand (259,200 for a 0.5 X 0.5 deg. grid) fields, each one being a point (cell or pixel) in a grid covering the entire earth.  Because each of these pixels has a value (e.g. oxisol or 1400 mm/yr) and because each plant also occupies a specific spatial position on earth (a pixel in our grid) we can find the range of soils or rainfall or any other spatial parameter occupied by that plant simply by having a database of localities (or pixels) in which it occurs.

Other Useful Programs

DECORANA - for correspondence analysis.
Component - for viewing cladograms and combining area with phylogeny cladograms
MacClade - nice user interface for mapping characters onto cladograms
Bioclim/Anuclim - for predicting ranges
Flora Map - for predicting ranges