Geology Reference
In-Depth Information
similis and anckelmani groups combined, the
sanaos group, consists of two species of lowland
forest disributed from West Africa to west
Kenya. In the three remaining Biyclus species,
each belonging to another species group, we must
suppose a habitat change, either from forest or
from woodland to montane forest, during their
evoluion. The nireus species group of the genus
Papilio shows a similar pattern, i.e. there are some
species whose sister species lives in montane for-
est (honimani-charopus-mackinnoni, esmondi-
thuraui), and some other species (aethiopsis, ch rap -
kowskii) whose sister species flies at lower eleva-
ions, either in forest or (also) in woodland.
Anicipating a study on the phylogeny of the
genus Metisella it can be said that the 13 species
listed in Appendix 8.2 fall into a number of spe-
cies groups which are enirely resricted to mon-
tane forests. Since the genus is sill under study
details cannot be given. Also in the genus
Uranothauma, with 12 of the 18 known species
restricted to the montane forests of EAT, diversi-
ficaion apparently took place largely within the
montane forest area. In all other genera either the
situaion is not clear or a habitat switch was
involved. In a number of genera the switch is clear
even without knowing the sister species, since
there are no other congeneric montane forest spe-
cies. This is paricularly the case in the genus
Colotis, where e/gonensis is the only forest species
while the 41 other species in Africa live in open
and often dry habitats. Other apparent switches in
habitat preference are found in Abantis meru,
Ampittia paoa, Biy/us dentatus and Yp thima
a/bia. In these cases a switch must have been
made from woodland to montane forest since there
are no close relaives living in forests. In the other
genera the situaion is less clear, but since always,
except in monotypic genera, different habitat
preferences occur in the genera (of the 46 genera
represented, 13 are restricted to forest, including
lowland forest, the remaining genera also occur in
woodland and/or open habitats), at least the
change from low or medium to high levels must
often have been made. Clearly phylogeneic data
would be most helpful here to exactly determine
sister species and the ecological switches made.
sussion
Th e Cameroun conneaion
The predicted pattern in case of a coninuous
connection of montane forest biota beween EAT
and Cameroun shows a fauna that is similar at
both ends, with shared species or, in view of the
short time lapse, at most sister species. The pat-
tern found is different. Although there are shared
species, the Cameroun fauna is poor in com-
parison with the fauna in EAT. A coninuous
connecion would explain the shared species, but
not the absence in Cameroun of the other 90% of
the montane forest fauna of EAT. Moreover, as
already stated above when describing the
scenario, if there was a connection between
Cameroun and EAT, the montane forests in EAT
would also be interconnected, leading to a more
or less uniform fauna. In that case the species
shared with Cameroun should be rather evenly
distributed over the montane forests of EAT.
This is not the case (see Table 8.5). The patten
does, however, agree with the idea that there
never was a coninuous connecion, but that a
number of montane species with a wider ecologi-
cal tolerance could live at lower alitudes at a ime
when the fauna there was unsaturated and com-
peiion was low (Hedberg, 1969; Diamond &
Hamilton, 1980; Hamilton, 1982; de Jong, 1986).
The latter situaion could have eisted when the
forest after a period of restricion to refugia
rapidly expanded its area.
It is temping to conclude that Cameroun has
no montane forest butterflies of its own but
received them from EAT. Actually, however,
there is little evidence for or against this. The
shared species could have arisen in Cameroun
and migrated to the east. This would explain why
in EAT the shared species are mainly found in the
westen areas (see Table 8.5), but the uneven
distribuion of the shared species over he moun-
tains of EAT could also have quite a different
origin, i.e. because the montane forest fauna
never was evenly distributed in EAT (see below).
What militates against a Cameroun origin is that it
is difficult to understand why a poor fauna could
successfully penerate into a much richer auna
and not vice versa. So far an easten origin of the
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