Selective Mating as a Factor for Speciation in Cichlid Fish of East African Lakes

Abstract

IN most of the modern texts on evolution¹, one of the outstanding proofs of speciation, that is, development of forms separated from one another under normal conditions by their immiscibility, without geographical isolation, is the very high number of species and genera of the Cichlidæ in almost every one of the great lakes in East Africa. This remarkable phenomenon (Woltereck's “schizotypische Artaufspaltung”) is characteristic only for the Cichlidæ of the East African lakes; other genera of freshwater fish can be represented in the same area also by more than one species, but in no other family is the diversity of types—some of them being specialized to a certain mode of life and nutrition—so well developed as in the Cichlidæ.