Geography Reference
In-Depth Information
ent to reconcile both cladograms. AF, Africa; AUS, Australia; NA, North America; SA,
South America.
This method has been criticized for not considering host switching or dis-
persal (Page and Charleston 1998). Charleston (1998) developed a solution
using mathematical structures called “jungles” that contain all possible par-
tial orderings in which the associate cladogram may be tracked in the host
cladogram, considering codivergence, duplication, sorting, and host-switch-
ing events and all the existing known associations. When the costs are cal-
culated for each of these events, it is possible to find the subgraphs that cor-
respond to the least costly reconstructions of the association.
Huelsenbeck et al. (2000) stated that in inferring host-switching events,
it is assumed that the host and parasite cladograms are estimated without
error. They suggested that a Bayesian estimation can be used in models
where host-switching events are assumed to occur at a constant rate over
the entire evolutionary history of the association. This method provides in-
formation on the probability that an event of host switching is associated
with a particular pair of branches and reduces the possibility that a particular
phylogenetic hypothesis may be overturned if a reexamination of the group
results in a different cladogram.
Criscietal.(2000)discussedaproblemofthetreereconciliationanalysis
and dispersal-vicariance analysis: that they violate metricity when consid-
ering that duplications are less probable than vicariance events. Violation
of metricity assumes in the calculations the existence of a nonmetric space
whose geometric properties are difficult to explore. Dowling (2002) enumer-
ated some criticisms to the program TreeMap; the most important is that it
may overestimate duplications and underestimate dispersal.
Algorithm
The algorithm consists of the following steps (Crisci et al. 2000):
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. Superimpose each component of a cladogram on the components of the
other cladograms.
4. Assume maximum cospeciation and no dispersal, attributing the differen-
ces between the cladograms to duplication or extinction events.
