Geography Reference
In-Depth Information
According to Wojcicki and Brooks (2005), this algorithm is most useful as an
a posteriori method, but it is also superior to all previous a priori methods
because it does not specify costs, weights, or probabilities of any biogeo-
graphic process. Brooks (2005) wrote that PACT works implicitly under the
taxon pulse model (Erwin 1979, 1981).
Algorithm
The algorithm consists of the following steps (Brooks 2005; Wo-
jcicki and Brooks 2004, 2005):
1. Obtain the taxonomic cladograms of the taxa distributed in the areas ana-
lyzed.
2. Replace the terminal taxa from the taxonomic cladograms with the areas
inhabited by them to obtain taxon-area cladograms.
3. Convert the taxon area cladograms into Venn diagrams and represent
them in parenthetic format.
4. Choose any taxon-area cladogram and determine its elements (compon-
ents and terminal taxa). It will be the template area cladogram.
5. Select a second taxon-area cladogram and determine its elements as in
the template area cladogram, and document which elements occur in the
latter (denoted by
Y
) and which do not (denoted by
N
). Each
Y
represents
a match with a previous pattern and is combined, whereas each
N
repres-
ents a new element and is attached to the template cladogram at the com-
ponent where it is linked with a
Y
. This requires two rules: (1)
Y
+
Y
=
Y
(combine common elements), as long as they are connected at the same
component; and (2)
Y
+
N
=
YN
(add new elements to the template area
cladogram at the component where they first appear).
6. When the new elements from the second taxon-area cladogram have
been added to the template area cladogram, see whether any of them can
be further combined. This requires three rules: (1)
Y
(
Y
-) =
Y
(
Y
-) (do not
combine
Y
s if they are attached at different components on the template
area cladogram); (2)
Y
+
YN
=
YN
(
Y
is part of
YN
); and (3)
YN
+
YN
=
YNN
(
Y
is the same for each, but each
N
is different).
7. Repeat steps 5 and 6 to incorporate all available taxon-area cladograms
in order to obtain the general area cladogram(s).
Software
Software for PACT (Wojcicki and Brooks 2004, 2005) is under de-
velopment.
