Population genetic structure of the perlemoen Haliotis midae in South Africa: Evidence of range expansion and founder events

Genetic diversity in Haliotis midae, a highly valued and heavily exploited marine gastropod, was assessed using 3 marker types across samples from the species' range in South Africa. Variation was compared at 7 allozyme loci, 2 regions of mitochondrial DNA and 3 microsatellite loci. We conclude that populations of H. midae on either side of Cape Agulhas represent 2 independent reproductive stocks. The area of transition between the stocks coincides with oceanographic features of the region. Evidence from all 3 types of genetic marker indicates an isolated introduction event to the east of Cape Agulhas, and subsequent range expansion in an easterly direction. The disparity between allozyme data and the other 2 forms is seen as further evidence for the presence of balancing selection at allozyme loci.