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Norris, in his revision of Malapteruridae, makes the statement that biogeographically, Lake Tanganyika is part of the Congo system and displays the same high level of endemism as the former.

I found that a thought-provoking comment, which made me look at African biogeography in a new light. I knew that Livingsone, Stanley et. al. were wrong in thnking of LT as the source of the Nile, but I didn't think of it as part of the Congo either. Not sure I really understand Norris, though, because (1) afaik, there aren't a lot of interconnections between LT and the R. Congo (am I wrong? Were there such in geological time?), and if LT is Congo, then where do the other Rift Lakes belong? Also Congo? (2) since the endemic species are distinct to each, I'm not sure I understand the significance of high endemism in both. What kind of relationship between high endemism and being part of the same system is being posited by Norris here?

I'm also a bit surprised that his "Sudanic" (not looking at the book right now, that may not be the exact term he uses) biogeographical region extends in a belt all the way from the Nile across to West Africa. Then there are two separate West African regions.

Anyone have any insights?

Dinyar

Lake Tanganyika IS connected to the Congo River drainage (via the Lukuga River, a tributary of the Lualaba River, itself part of the Congo River drainage), although fish can no longer freely swim across the two water bodies (although they may have in the geological past).

As for the biogeographic region you are talking about, it's the Nilo-Sudanic system, and it includes the Niger River drainage in west Africa, because the drainages were connected historically. Evidence of this connection can be seen in the fact that some catfish groups (e.g. <i>Mochokus</i>) are found only in drainages of the Nilo-Sudanian system.

And no, there is only one West Africa ichthyologically speaking (the western part of the Nilo-Sudanian system). The Congo River drainages and the Zaire system it represents, is more accurately termed West-Central Africa.

There's still very little we know of African freshwater fish zoogeography. Humphrey Greenwood once said that we have not moved beyond the "bioaccountancy" stage in this respect, and I tend to agree with him.