Neologist, I assume you were asking about the following?
Quote: Can the cichlid from one side of the rift successfully mate with the cichlid from the other side of the rift?
. The concet of species states that a single species is a population of organisms that will freely reproduce within that population. Species may be composed of multiple populations but if they freely interbreed (like basenjis from Egypt will breed with basenjis from Brooklyn). They fit into a same species.
The cichlids from the various lakes and the Nile dont interbreed freely, they occupy different niches, have many morphological differences, and many are actually active at different times of the day. Considering that the cichlids have differentiated themselves to the genus level, they have gone and evolved at collective morphological levels that assign the newer species to even different genera.
Remember, in the Linnean system we have
KINGDOM
PHYLUM||
CLASS
ORDER
FAMILY
GENUS
SPECIES
Of all the above organizational groups, only species has a clear testable definition, all the higher categories are (usually) based upon morphological variations
SO, no , the Nile , Turkana,Malawy, Victoria, , Ziway etc cichlids are not free interbreeders . Having said that, Im sure that aquarists have force bred hybrids of different genera and produced something. Just like a Tigron is an artificially bred cross between a lion and tiger. Usually though, such animals are sterile.
So, my answer is that these fish dont interbreed, as separate species and genera, they are, by definition sexually isolated.