Testing Relationships Between Biotic Components - Evolutionary Biogeography - page 185

ate historical episode. Ambiguous areas should be duplicated until as-
sumption 0 is satisfied.
• The “Threes Rule”: In order to distinguish between general and special
patterns of historical association based solely on the available data,
and, in particular, to determine whether absence from an area is due
to secondary extinction or primitive absence, at least three co-occur-
ring clades must be analyzed.
Primary BPA is exemplified in fig. 5.9 . Four taxon-area cladograms ( figs.
5.9a - 5.9d ) are analyzed, and a data matrix is derived from the information
obtained from them ( fig. 5.9e ) . The parsimony analysis of the data matrix
results in a single general area cladogram ( fig. 5.9f ) . In the general area
cladogram, there are four parallelisms involving North America and Africa
(component 8) and Africa and South America (component 9). For secondary
BPA a new data matrix is constructed ( fig. 5.10a ), where Africa is treated as
three different areas: Africa' represents the original congruent relationship of
Africa with the remaining areas, and Africa'' and Africa''' represent the incon-
gruent relationships due to components 8 and 9, respectively. The analysis
of this data matrix results in a single general area cladogram, where Africa',
Africa'', and Africa''' appear in three different positions, depicting the falsific-
ations of the null hypothesis of vicariance.