Small but significant differences were found in allele frequencies among five populations
(overall F-ST estimate (theta)=0.004, P=0.006; overall F-ST estimate (RHO)=0.019,
P <0.00001) of the demersal cichlid Copadichromis sp. 'virginalis kajose',
collected from five locations in Lake Malawi. Pairwise FST estimates revealed significant
differences between the most southerly population (Cape Maclear), and the three most
northerly populations (Mbamba Bay, Metangula and Chilola). Pairwise F-ST estimates also
revealed significant differences between some populations, but no geographical pattern was
discernible. There was no evidence of isolation by distance using either the shortest
straight-line distance between samples, or the distance around the shoreline following a
50 m depth contour. F-ST estimates were considerably lower than found in previous studies
on the mbuna (rock-dwelling species), but higher than those found in a study of three
pelagic cichlid species from Lake Malawi. Substructuring in C. sp. 'virginalis kajose'
appears to be on a similar scale to the Atlantic cod.