Historical Biogeography: Introduction to Methods

The five basic historical biogeographic methods are: dispersalism, phylogenetic biogeography, panbiogeography, cladistic biogeography, and parsimony analysis of endemicity. Dispersalism derives from the traditional concepts of center of origin and dispersal. Bremer's recent cladistic implementation of dispersalism estimates the relative probability that different areas were part of the ancestral distribution of a group. Phylogenetic biogeography applies the rules of progression and deviation to elucidate the history of the geographical distribution of a group. Panbiogeography consists of plotting distributions of different taxa on maps, connecting their distribution areas together with lines called individual tracks, and looking for coincidence among individual tracks to determine generalized tracks. Generalized tracks indicate the preexistence of widespread ancestral biotas, subsequently fragmented by geological or climatic changes. Cladistic biogeography assumes a correspondence between taxonomic relationships and area relationships, where comparisons between area cladograms derived from different taxa allow one to obtain general area cladograms. The most important cladistic biogeographic procedures are: component analysis, Brooks parsimony analysis, three-area statements, and reconciled trees. Parsimony analysis of endemicity (PAE) classifies areas by their shared taxa, analogous to characters, according to the most parsimonious solution. We think the various methods are not mutually-exclusive alternatives, but some of them can be integrated in a single biogeographic approach, with the capability of resolving different problems, such as the recognition of spatial homology (panbiogeography), the identification of areas of endemism (PAE), and the formulation of hypotheses about area relationships (cladistic biogeography).