Geography Reference
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how many times they are represented in it. The deficiencies of this revived
dispersalism, which ignores homology and uses paralogy to weigh areas
and locate centers of origin, have been demonstrated eloquently by Ebach
(1999). Simply by weighting replicated areas in basal clades, these methods
overestimate the areas where there were fewer extinctions but fail to identify
an area as ancestral. Thus they expose the main defect of the dispersal-
ist approach: that the centers of origin are an artifact of paralogy (Morrone
2002b). Ancestral area analysis represents a common misapplication of a
cladistic method to a biogeographic problem (Parenti and Humphries 2004).
The optimization of areas on the internal nodes of an area cladogram to in-
terpret the ancestral area or center of origin is inappropriate because it dis-
misses vicariance and favors implicitly the hypothesis of a center of origin.
In fact, this misinterpretation becomes evident when authors refer to “basal”
or “early divergent” extant taxa (Crisp and Cook 2005; Santos 2007). Area
cladograms are biogeographic classifications, not explicit evolutionary hypo-
theses.
Willi Hennig (1913-1976), a German entomologist, is best known as the
father of phylogenetic systematics or cladistics, which had profound effects
on the theory and practice of systematics (Nelson and Platnick 1981; Wiley
1981). Hennig (1950) described four criteria for determining character po-
larity: geological precedence, chorological precedence, ontogenetic preced-
ence, and correlation of transformation series. The second combines the
phylogeny of a monophyletic group with the distribution of its species to
trace the progression in space.
Phylogenetic biogeography applies two rules. The chorological progres-
sion rule assumes a progression in the areas parallel to the progression in
thecharactersinthecladogram,sothattheareasinhabitedbyprimitivespe-
ciesaredeemedtobeancestral, whereasthe areasinhabited byapomorph-
ic species are situated far away from the center of origin. The deviation rule
states that in every speciation event one sister species is more apomorph-
ic (“deviated”) than the other, which remains more similar to the ancestor.
These rules are based on the assumption that the peripatric speciation mod-
el is common in nature. If this speciation model occurs again and again, we
will have the impression of dispersal from one area to another.
