Geography Reference
In-Depth Information
Figure 5.1
Steps of a cladistic biogeographic analysis. (a-c) Three taxonomic
cladograms; (d-f) maps showing the distribution of the species of the three taxa
analyzed; (g-i) taxon-area cladograms; (j-l) resolved area cladograms; (m) general
area cladogram.
The construction of taxon-area cladograms is simple when each taxon is
endemic to a single area and each area has only one taxon, but it is more
complex when taxonomic cladograms include widespread taxa, redundant
distributions, and missing areas. In these cases, some methods require that
taxon-area cladograms be turned into resolved area cladograms (Crisci et
al. 2000; Morrone 1997; Morrone and Carpenter 1994; Morrone and Crisci
1995; Nelson 1984; Nelson and Platnick 1981; Page 1988; Sanmartín and
Ronquist 2002; Warren and Crother 2001). These are also known as fun-
damental area cladograms (Nelson and Platnick 1981), area cladograms
(Page 1990a), and areagrams (Ebach et al. 2005a; Swenson et al. 2001;
van Welzen 1992).
Widespread Taxa
Whenanyoftheterminaltaxaofataxon-areacladogram
inhabits two or more of the studied areas, it is a widespread taxon (Nelson
and Platnick 1981) or a mast (for “multiple areas on a single terminal”)
(Ebach et al. 2005a). For example, if a taxon (1 (2, 3)) has species 1 dis-
tributed in both North America and Africa, species 2 in South America, and
species 3 in Australia, by replacing the three species in the cladogram by
the areas where they are distributed, we obtain the taxon-area cladogram
(North America-Africa (South America, Australia)). As a result of the wide-
spread taxon, North America and Africa appear together in the taxon-area
cladogram.
Under assumption 0 (Zandee and Roos 1987), the areas inhabited by a
widespread taxon are considered as a monophyletic group in the resolved
areacladogram,meaningthatthetaxonistreatedasasynapomorphyofthe
areas. Under assumption 1 (Nelson and Platnick 1981), the widespread tax-
on is not considered as a synapomorphy in constructing the resolved area
cladograms, and the areas inhabited by it can constitute monophyletic or
paraphyletic groups in the resolved area cladograms. Under assumption 2
(Nelson and Platnick 1981), only one of the occurrences is considered as
evidence, whereas the other can “float” in the resolved area cladograms,
thereforeconstitutingtheareasinvolvedmonophyletic,paraphyletic,orpoly-
