MORPHOLOGICAL AND GENETIC DIFFERENTIATION OF PATELLA-GUANULARIS (GASTROPODA, PATELLIDAE) - RECOGNITION OF 2 SIBLING SPECIES ALONG THE COASTOF SOUTHERN AFRICA

Morphological and isozyme variations between 13 populations of the spe cies hitherto named Patella granularis were investigated to see whethe r differences in shell structure between the west coast versus the sou th and east coasts of southern Africa are supported by other morpholog ical features or by genetic differences. The shells showed a definite decrease in size from west to east, but this is correlated with produc tivity and is of no diagnostic use in distinguishing between populatio ns. Discriminant functions analysis based on shell morphometrics faile d to separate populations from the three coastal regions. Shells from the northern east coast do, however, have shell nodules with a dark pi gmentation, distinctly separating them from those further south and we st. No differences in radular or soft part morphology were detected be tween the populations, but the four northernmost populations on the ea st coast have a significantly shorter Z looping of the gut than the ot her populations along the coast. Significant microstructural differenc es in the sperm were also detected between these two groups of populat ions. Electrophoretic analysis of 16 enzyme loci failed to detect any significant differences between the west and south coast populations, but revealed a genetic identity (Nei) of 0.528 as well as four diagnos tic alleles between the four northernmost populations from the east co ast compared with those to the south and west. The two genetically dis tinct forms occurred sympatrically at one of the study sites on the ea st coast (Coffee Bay). It was concluded the two groupings were suffici ently different to warrant the recognition of a separate species, whic h is centred in KwaZulu-Natal on the east coast and extends south to C offee Bay, from where it is replaced by P. granularis. There is, howev er, no evidence at all that the west coast populations are in any way separable from the remaining populations of P. granularis on the south coast.