Boundaries

This ecoregion is defined by the Fouta Djalon plateau and is distinguished by an endemic aquatic fauna adapted to its headwater streams. Isolation of individual rivers, stability over geologic time, and numerous waterfalls and rapids that have restricted colonization by downstream species are believed to have encouraged the evolution of a high number of species restricted to the rivers draining the plateau. The vast majority of the plateau and the lower plains of Gaoual and Koundara are within Guinea.

Topography

The area is characterized by sections of blocky, elevated plateau (about 600 – 1,500 m) separated by deep gorges through which rivers and streams descend to the coast or to feed larger rivers inland (Daget 1962). Several of the important mountainous areas within the Fouta Djalon include Mont Loura(Mali), Fello Digui (Gaoual), Fello Sounga (Gaoual), and the raised edge of the piedmont (DNE et al. 1999; Bazzo 2000). Mont Lora is the highest peak in the region (1,538 m).

Freshwater habitats

Flooding is intense during the wet season when large amounts of rain fall in a short period of time. However, due to the great age of the plateau and its well-weathered nature, sediment load is relatively low. The aquatic organisms of the plateau are adapted to periods of intense flooding followed by months with no rain, and thus, declining water levels.

Terrestrial habitats

The Fouta Djalon plateau is surrounded by a zone of forest/savanna transition, but the upland areas of the plateau are dominated by submontane vegetation, including the most prevalent species, Guinea plum tree (Parinari excelsa), and Parkia biglobasa (Martin 1991; Sayer et al. 1992). There is hardly any forest on the massif apart from some small relatively well-preserved forest reserves, and a 4.5 km² pine plantation at Dalaba (DNE et al. 1999). The aquatic vegetation is dominated mainly by Marantacea and Cyperacea. The rivers are often bordered by a forest gallery with Pandanus. Grasses bordering the rivers are dominated by Hyparrhennia, Andropogon and Pennisetum. In many areas, the remaining forests constitute patches in the headwaters, galleries along the rivers and scattered trees on the floodplains.

Description of endemic fishes

About one-quarter of the sixty described fish species in the ecoregion are endemic. Nearly all of the endemic species are cyprinids and most of these are barbs. 

Justification for delineation

Several factors facilitated evolution of the endemic fish fauna: individual rivers are extremely isolated from one another by the plateau; numerous waterfalls and rapids occur along their course, providing further isolation of headwater faunas from potential downstream colonists; and the cooler conditions afforded by the higher altitude of the plateau may have offered a refuge during periods of warming and desiccation at lower elevations. Initial uplifting in the late Jurassic created the Fouta Djalon plateau. In the Miocene, tectonic movements caused further uplifting, and the plateau has been relatively stable since that time. The plateau, as part of the Guinean range, has acted as a barrier to movements of aquatic species across it. For example, there are only a few fish species that are known from both slopes of the Fouta Djalon: Amphilius rheophilus and A. platychir, as well as Barbus cadenati, B. guineensis and B. dialonensis (Lévêque 1997). In general, the fish fauna has affinities with the Upper Guinea bioregion.

Level of taxonomic exploration

Fair. Intensified data collection is needed.