In a study of cichlid fish inhabiting Lake Victoria in Africa, researchers examined presumably neutral sequence polymorphisms thought to be located in noncoding genomic loci in 12 lake species and their putative riverine ancestors (Nagl et al. 1998. Proc. Natl. Acad. Sci. [USA] 95: 14,238–14,243). At all loci, the same polymorphism was found in nearly all of the tested species from Lake Victoria, both lacustrine and riverine. Different polymorphisms at these loci were found in cichlids at other African lakes.
(a) Why would you suspect neutral sequences to be located in noncoding genomic regions?
( b) What conclusions can be drawn from these polymorphism data in terms of cichlid ancestry in these lakes?
