The montane butterflies of the eastern Afrotropics - Biogeography and Ecology of the Rain Forests of Eastern Africa - page 138

live on Viola, usually occur not far from the forest.
Similarly one can argue about the inclusion or
exclusion of Aloeides species. A few of the 43 spe-
cies of this essenially South African genus occur
in grasslands in EAT. A. conradsi, for instance,
can be common in montane grassland near
Maralal (N Kenya) at 2000 m (R. de J., personal
observaions). Since the species concened can
also occur at lower levels and may be found in
open woodland as well, they have been left out.
Inclusion of such species would obscure the
history of the strictly montane species.
While selecing potenial areas of endemism we
have chosen the same mountains or mountain
ranges for the grassland and the forest butterflies
to facilitate comparison between the two. Not all
mountains, however, carry montane grassland. It
is, for instance, absent from Usambara, Nguu and
Nguru. It is, therefore, not surprising that no
endemic grassland butterflies are found there.

cies than the woodlands where most species are
the same as at lower elevaions.
The montane grassland is difficult to delimit
exactly. Not only is the lower limit often obscure,
but the grassland may also gradually merge into
open woodland and other types of open vegeta-
ion. Near Maraia! (N Kenya), for example, there
are wide stretches of grassland along the eastern
rim of the Rift Valley, at over 2000 m. This grass-
land is gradually replaced locally by more or less
open]unipe
u

s and Poocarpus forest, and south of
Maraia! it descends to lower elevations and
changes into Acacia savanna. As a consequence
areas of montane grassland are usually not much
isolated from each other and are often intercon-
nected by other types of open formaions.
Moreover, although part of the montane grass-
lands must be natural, their extent has been
greatly enlarged by human aciviies (Kielland,
1978; Hamilton, 1982) thus increasing the possi-
bility of interchange for the species restricted to
this habitat. It is therefore not surprising that
endemism in this habitat is rather low in EAT.
The situaion is different in South Africa where
there is a better developed grassland fauna with
many endemic species, especially in the
Lycaenidae; for example, the genus Thestor num-
bers 23 species which are all restricted to the
Cape Province except for two species which reach
Transvaal.
An interesing ecological feature of the grass-
lands is that they are often bunt at the start of the
dry season. Although this may often or even usu-
ally be atributable to human interference natural
fires also occur. A number of plant species
depend on the fires and do not appear if the grass
remains unbunt. Butterflies dependent on these
herbs (and thus also on the fires), like Lpido-
chysops species (Lycaenidae), tend to have a very
short season in August and September. At this
ime of the year night temperatures can fall below
freezing point. Windswept, fire-blackened stubble
in the coldest, driest ime of the year can be an
inhospitable habitat.
It is not always easy to decide if a species is
characteristic for grassland. Some of the species
selected may not be strictly grassland species; for
example, the Issoia species, the larvae of which

Scenarios and predied patens

Since the present extent of the montane grass-
lands has been so srongly enlarged by human
aciviies it is uncertain if the grasslands ever were
more extensive than at present even when mon-
tane conditions were more widespread. This
makes it difficult to frame hypotheses. In conrast
to the montane forest, there was (and is) no
reservoir of grassland species to the west. The
only area in Africa with a well-developed montane
grassland fauna is South Africa. So as a start we
may consider the following opions:

1. South African connecion. The montane
grassland butterflies of EAT originated
from a South African fauna that once
expanded its range to the north and later
became isolated there. This leads to a
recurrent pattern of sister-group
relaionships between taxa in EAT and
South Africa, and of taxa (be it
subspecies, species, or monophyleic
groups) covering all or most of the
available habitats in EAT.
2. South African connecion. The South
African species expanded northward by