Geography Reference
In-Depth Information
Salazar (2005), Riddle and Hafner (2006), Rode and Lieberman (2005), Sid-
dall and Perkins (2003), Taberlet et al. (1998), van Soest and Hajdu (1997),
van Veller et al. (2000), Van Welzen et al. (2003), and Wiley (1987, 1988a,
1988b).
Several biotic patterns are known for the African forest biota, with disjunct mont-
ane and alpine forest “islands” surrounded by lowland forest. The origin of these
patterns has been traditionally attributed to climatic changes. Griswold (1991) un-
dertook a cladistic biogeographic analysis based on spider forest taxa.
Griswold (1991) analyzed four taxa for which phylogenetic hypotheses were
available: the genus
Microstigmata
(Microstigmatidae), the tribes Vidoleini and
Phyxelidini (Amaurobiidae), and the
Moggridea quercina
species group (Migidae).
He selected nine areas of endemism: Table Mountains, Knysna Forest,
Natal-Zululand Coast, Transkei-Natal midlands, Natal Drakensberg, Transvaal
Drakensberg, Eastern Arc Mountains, East African volcanoes, and central Mad-
agascar (
fig. 5.11a
)
. The author applied Kluge's (1988) implementation of BPA,
constructing a data matrix of nine areas by seventeen components, which he ana-
lyzed with Hennig86 (Farris 1988).
The analysis of the data matrix gave eight general area cladograms of twenty-
one steps, a consistency index of 0.80, and a retention index of 0.77. The clado-
grams were identical except for the placement of the Natal-Zululand Coast, which
could be placed at different positions (
fig. 5.11b
). The basal dichotomy leads to
the Cape region of South Africa (Table Mountains and Knysna Forest) and the
remainder of continental Africa plus Madagascar. A region south of the Limpopo
River Basin in northern Africa (Transvaal Drakensberg) shows affinities with trop-
ical Africa (Eastern Arc Mountains), East African volcanoes, and central Madagas-
car. Eastern South Africa (Natal-Zululand Coast, Transkei-Natal midlands, and
Natal Drakensberg) is related to tropical Africa and Madagascar rather than to
the nearby Cape region. Two upland areas (Transkei-Natal midlands and Natal
Drakensberg) are sister areas. The most striking result is that central Madagascar
is related to eastern Africa (Eastern Arc Mountains and East African volcanoes)
rather than being the sister area to all Africa.
Griswold (1991) suggested that the general area cladogram was difficult to re-
concile with a historical scenario involving primarily Pleistocene vicariance events.
On one hand, a Pleistocene vicariance scenario in which forests expanded and
contracted may suggest that geographic proximity should be a good predictor of
sister area relationships, which was not the case. On the other hand, the sister
area relationship between Madagascar and East Africa led Griswold (1991) to hy-
pothesize a greater age for the taxa involved, probably Mesozoic.
