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The inland water fishes of Africa

 | 
Didier Paugy
, 
Christian Levêque
, 
Olga Otero

Biogeography and past history of ichthyological faunas

Christian Levêque und Didier Paugy

Zusammenfassung

Ichthyological faunas established themselves and evolved as a consequence of the history of the aquatic systems they occupy. At various timescales, certain basins were colonized from other basins, and such colonizations were sometimes followed by selective extinctions resulting from geological and/or climatic events. The genesis and continued existence of aquatic habitats depend on two main factors: their morphology, which may change over the long term as a result of erosion or tectonics; and their hydrologic budget, which is dependent on precipitation, evaporation, infiltration, and for which slight changes may lead in the short or medium-term to either the drying out or expansion of the aquatic milieu in question, depending on the basin’s shape. Simultaneously, some species were able to give rise to others, and these speciation events often explain the presence of centres of endemism.
Biogeography is the discipline that seeks to explain the distribution of organisms and the relationships between the areas of distribution of different species, by attempting to reconstruct the series of events that led to the present situation. To describe the relationships between the establishment of faunas and the spatio-temporal history of the physical systems, scientists need to draw up the most exhaustive inventories possible for different regions.

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How do fish disperse?

Given that the large majority of fishes cannot tolerate exundation, the colonization of new habitats is made possible by the existence of connections between basins. Even if hydrographic systems are currently isolated, such connections may have existed in the past, allowing faunistic exchanges.

Connections between river basins

The great similarity between the faunas of the Nile and Chad Basins is undoubtedly the result of connections that existed between the two basins during a humid period that is difficult to date (Lévêque, 1997a). Meanwhile, a connection still exists between the Chad and Niger basins. When water levels are high, some of the waters of the Logone, a tributary of the Chari, spill westward into the Mayo-Kebi depression, cross the Gauthiot falls, and empty into the Benue, a tributary of the Niger River.

The regressive erosion that led to the capture of certain watercourses was probably the most important means of interbasin exchanges for “primary” fi...

Autoren

Research director at IRD. He has published numerous works on the systematics, distribution, and ecology of West African fresh water fishes, and expanded the collections of the MNHN in Paris.

Research director at IRD. He has published numerous works on the systematics, distribution, and ecology of West African fresh water fishes, and expanded the collections of the MNHN in Paris.

© IRD Éditions, 2017

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