Geology Reference
In-Depth Information
predaion; or bongo and giant hog such eposure
could have been criical to survival.
The number of mammal species within any one
forest block is likely to have a relaionship to (i)
the overall area of forest,
(iii)
its ecological diver-
sity, (iii) its climaic histoy, especially its relaive
stabiliy in the past and (iv) its human history,
especially past populaion density and huning
pressure. Thus the Uzungwa forests, which cover
the largest area and a broad specrum of alitudes
and edaphic condiions, have a more diverse
mammal community. This is most evident in
primates, where the Sanje mangabey and red col-
obus occur together with he more widely dis-
ributed guenons and pied colobus and in the
occurrence of exclusively forest species such as
the servaline genet, Genetta seoalina lowei.
areas of formerly dry couny by forest would have
selected for many arid country species to adapt to
the new condiions. This would afect local
populaions in speciic localiies as well as larger
populaions across very broad fronts running all
the way between the Atlanic and Indian Ocean
shores. Cycles of afforestaion in central Africa
and especially over the Zaire basin would have
been comprehensive and their effect on mammal
populaions would have been correspondingly
extensive.
Similar developments along the easten sea-
board would have been synchronised but less
extensive in scope, and only a few populaions
would have connected up with their westen
counterparts during each climatic pulse. Would
the frequent recurrence of comprehensive
reafforestaion over cenral Africa have exerted
more pressure for adapive change? Could easten
populaions have remained geneically less
advanced because they were detached from such
developments? There certainly appear to be
several easten species that are more conservaive
in their adaptaions than their westen
equivalents.
Consider some of the pairs listed in Table 11.3.
Dendrohyrx dorsalis is a long-limbed, enirely
arboreal lowland forest animal with a long skull
and muzzle. By contrast, D. validus shows propor-
ions that are closer to those of the more ter-
restrial Heterohyrax and Procavia. The adopion of
arboreal habits appears to be a late and advanced
condiion in hyraxes. It is therefore striking that
he diverse origins of easten endemics
The Guineo-Congolian rain forest block may not
be the only source of mammal fauna in easten
Tanzania. It is likely hat many forest organisms
derive from more arid habitats and it is possible
that the easten orests retain populaions in
which adaptaion to forest-dwelling is less
advanced than in closely related types that live
urther to he west. If this is so, it invests the
Tanzanian forest communiies with some poten-
ial for an understanding of how non-forest
organisms adapt to moister condiions as well as
forest forms coping with drier regimes.
During vey moist periods, engulfment of large
Table 11.3. Wes tn orest equivalents of Easten orest nemic mammal sp ecies
Westen equivalents of related orms
Eastern endemics
Perodiaius potto
(possible equivalent)
Ga/ago inustus
Dendrohyrx orsalis
Numerous specialist forms of squirrels
Cicetomys emini
more wholly
arboreal Praomys
spp.
other
hamnomys
spp.
Bdeoga/e niipes
Neotraus batesi
Cpha/phus al/ipyu s
and
.
nigirons
Ga/ago ganetti
Ga/ago zanzibaricus
Dendrohyrax validus
Funisciurus palliatus/lucife r
(medium-sized generalized complex)
Cricetomys cosensi
and
Beamys hindei
Praomys eleaorum
hamnomys cometes
Beogale crssicaua
Neotraus moschatus
Cphalophus havyi
and
.
natalensis
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