Boundaries

The Mulanje Massif defines the boundaries of this ecoregion, whose headwater streams are isolated from downstream reaches by waterfalls, such that several endemic and relict species occur in and along these highland rivers. The massif is a huge, isolated block of mountains, more than 640 km² in extent, situated in the southeast corner of Malawi close to the Mozambique border (Eastwood 1979).

Topography

The massif rises abruptly from the flat Phalombe plain (600 m above sea level), to a plateau at nearly 2,000 m, and then up to rocky peaks reaching 3,002 m.

Freshwater habitats

The Phalombe plain is heavily populated and used extensively for agriculture. To the south of the mountain, the Lower Shire rift escarpment causes the Ruo River to drop rapidly to around sea level. This descent includes the 60 m-high Zoa Falls, which effectively isolate the Ruo River fish fauna from the Lower Zambezi fauna found in the lower reaches of the Ruo and in the Lower Shire. The area to the east of Mulanje in Mozambique is poorly known. Isolated smaller mountains in the area may have similar aquatic faunal characteristics to Mulanje.

Description of endemic fishes

In the Ruo River from the base of the plateau to Zoa Falls, at least ten fish species out of 37 recorded are not found in neighbouring river systems, including at least six probable endemics that are currently under investigation (Tweddle (Tweddle 1985; Tweddle unpublished data; Tweddle & Skelton 1998). Sampling in nearby Mozambique streams that drain to the East African coast is needed to verify the endemism of the Ruo River species. 

Several relict fish species occur in the Ruo as well as in other Zambezi tributaries. These include Hippopotamyrus ansorgii, Barbus eutaenia, B. lineomaculatus,and Opsaridium zambezense. The perennial nature of the streams flowing from the southern slopes of the massif, and the barrier to upstream movement created by Zoa Falls, have allowed the long term survival of a fish fauna that now shows major differences to those of neighboring river systems.

The northern streams from the massif do not contain any endemic fish species, though some have still to be described (Tweddle 1979). These perennial streams form a valuable refuge for the Lake Chilwa fauna during the periodic drying out of the lake (Kalk et al. 1979).

Justification for delineation

The massif is a quartz-syenite and granitic plutonic intrusion(s), uplifted, fractured and eroded. Larger river valleys are truncated at the edge of the plateau, forming high waterfalls. Waterfalls on the Ruo River, for example, descend 200 m in a single fall. The plateau is surrounded on many sides by sheer rock walls up to 1,700 m in height (Chapman 1962; Dudley 2000). Floristically, Mulanje belongs to the Afro-montane regional centre of endemism (White 1983).

Level of taxonomic exploration

Fair. The fish fauna is generally well known, though further sampling is needed as some species are known only from few specimens (one each in the case of two unidentified Barbus species). Dudley (2000) summarizes information on all other flora and fauna and points out that many groups are poorly collected; further research on these taxa is essential, preferably under the umbrella of the Conservation Trust.