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flies of these habitats may have a different history
from the forest species. They will be briefly dealt
with as an illustration ofthe complex and dynamic
character of the butterfly fauna of the African
mountains, but their numbers are low ifcompared
with the rich forest fauna.
The area covered in this chapter is the easten
half of Africa, east of the Congo basin, and from
the highlands of Ethiopia in the north to the Zam-
bezi River in the south. We have termed this area
'Easten Afrotropics' (abbreviated EAT), so as to
avoid confusion with the term 'Easten Africa'
which is used in this topic to cover a more restric-
ted area. The mountains in this area are complex
and consist of ranges of widely different geologi-
cal origin and age. It would not be possible to deal
adequately with all mountains in a single chapter.
Therefore we shall make a selecion and leave a
number ofmountains such as Marsabit, Kulal and
Karisia Hills in N Kenya and the Taita Hills in
SE Kenya out of consideraion, except where they
may be of assistance in a discussion. Some other,
complex mountain ranges are taken as a single
range here for the sake of convenience, e.g.
'Ethiopia' (see Hamilton, 1982, fig. 53 for the
disjunct nature of the mountain forest in Ethio-
pia). We do not think this detrimental to our
conclusions.
Old mountains are found in the so-called
Easten Arc. These mountains run in a broad arc
through easten Tanzania from the Pare Moun-
tains in the north near the Kenya border through
the Usambaras, Nguu, Nguru, Ukaguru, Rubeho,
Uluguru and Uzungwa to the Southen High-
lands (Figure 8.1). The mountain range coninues
southward into Malawi (Nyika Plateau and fur-
ther south). To the north, the Taita Hills in
Kenya belong to the same formaion. They con-
sist of ancient basement and crystalline rocks at
least 1 600 million years old. They were, however,
not uplifted all at the same ime. Some areas like
the Usambara and Uluguru mountains are sup-
posed to be ofJurassic age, while the Nguru and
Uzungwa mountains were the result of iling of
huge blocks at about the end of the Miocene
(around 12 Myr BP) (Moreau, 1966). Other,
higher mountains in East Africa came into being
during the
volcanoes Kilimanjaro, Mount Kenya and Mount
Elgon began to pile up and the gigantic block
Rwenzori started to rise. In the Pleistocene also,
the East African surface was not at rest. Rwenzori
coninued to rise, the Virunga Volcanoes north-
east of Lake Kivu and the Rungwe volcano at
the head of Lake Malawi (in contact with the
much older Southen Highlands), and the
volcanoes Kulal and Marsabit in north Kenya
were built up.
The complex geological history of the easten
half of Africa, combined with dramaic climaic
changes in the Pleistocene and coinciding with
the northen Ice Ages, renders the montane
habitats in EAT a potenially most interesing
subject for biogeographic analysis.
The mountains of EAT have been very dif-
fe rently studied regarding their butterfly popula-
ions. Many distribuional records of remote
mountain areas in west Tanzania (Ufipa,
Mpanda, Kigoma) and south and east Tanzania
(Eastern Arc mountains) have become available
only in recent years thanks to the indefaigable
efforts of J. Kielland.
Mehods
To find an answer to the quesion of the origin
and difereniaion of the montane butterfly auna
we shall describe several possible scenarios,
predict disribuion patterns on the basis of these
scenarios, and test the predictions against the
actual pattens found. An important tool would be
cladisic biogeography, in which similar sequen-
ial speciaion pattens in different groups are
used to frame hypotheses about the sequence of
connecions and disconnecions of areas. Pre-
requisite for the applicaion of this tool is the
availabiliy of well-supported. phylogenies. These
are extremely scarce for montane groups in EAT.
In the few instances that phylogenies of montane
butterflies are available, there is, moreover, so
much distribuional overlap that they are not very
helpful in this respect, but they are helpful in
others, for example by indicaing differeniaion
within Easten Africa and change of habitat pref-
erence. Vigorous as cladisic biogeography may
be, it also has its limitaions. For instance, it starts
Pliocene
when the
enormous
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