Geography Reference
In-Depth Information
dealtwith.Thethirdone,temporallypartitionedcomponentanalysis(TPCA),
is dealt with herein.
Upchurch and Hunn (2002) proposed this method, also known as chro-
nobiogeography, to incorporate explicitly temporal data into a cladistic
biogeographicanalysis(seealsoHunnandUpchurch2001andUpchurchet
al. 2002). After geodispersal, due to area coalescence events (biogeograph-
ic convergence), “the histories of areas and biotas will have a reticulated
rather than a branching structure, raising the question as to how well cladist-
ic biogeographic techniques will be able to accurately analyze and depict
a reticulate system” (Upchurch and Hunn 2002:280). In short, the starting
point of TPCA is the existence of taxon-area cladograms for the taxonomic
groups on which the analysis is based.
Although the introduction of time slicing may tend to uncover reticulate
histories, it is interesting to note that, ideally, synchronic relations would be
found for each time slice on the basis of phylogenetic relations. TPCA is a
pragmatic analytical method that allows reticulate histories to be explained,
where assumptions are minimized, and the area and lineage duplications
that may be produced by Brooks parsimony analysis are avoided.
Algorithm
It consists of the following steps (Upchurch and Hunn 2002):
1. Prune or temporally partition the taxon cladograms by deleting all taxa that
did not exist at a particular designated time slice.
2. Find optimal area cladograms for each particular time slice by determining
which area relationships provide the best (under some designated optim-
ality criterion) explanation for the spatial distributions observed in the tax-
on cladogram.
3. Use a randomization test to determine whether the degree of fit between
area and taxon cladogram for each time slice is greater than would be ex-
pected by chance.
Empirical Applications
Hunn and Upchurch (2001) and Upchurch and
Hunn (2002).
Dinosaurs were diverse, geographically widespread and stratigraphically long
lived terrestrial taxa, which provide an ideal case study for Mesozoic biogeo-
graphy. Some authors have proposed vicariance, driven by continental fragmenta-
