Geography Reference
In-Depth Information
taxon-area cladograms. Area cladistics begins by replacing the names of
the terminal taxa of two or more taxon-area cladograms and deriving are-
agrams and then resolves paralogy using the transparent method (Ebach et
al. 2005a). Areagrams of different taxa inhabiting the same areas are com-
bined, and patterns are searched (
fig. 5.22
). When geographic congruence
between the different areagrams is found, we may interpret the biotic his-
tory. Biotic congruence is evidence of vicariance, and we can infer that biotic
components inhabiting sister areas were once part of the same biotic com-
ponent, which posteriorly diverged.
Ebach and Humphries (2002) summarized the underlying rationale of
area cladistics with six axioms:
• An endemic area is the known distribution of a taxon.
• Congruence is a result of allopatric speciation, the direct or indirect
consequence of continental drift.
• The relationship of areas equates to the relative geographic proximity
of areas.
• Area cladistic data may not necessarily be consistent with other forms
of data.
• Sampling of different data sets will yield consistent results.
• Paleomagnetic and area cladistic data provide independent evidence
of continental drift.
Figure 5.22
Area cladistics. (a-c) Three taxon-area cladograms with paralogous
nodes, each showing the application of the transparent method; (d) general area
cladogram obtained.
