GENETIC AND MORPHOMETRIC VARIATION IN THE POTAMONAUTID RIVER CRAB POTAMONAUTES-PARVISPINA (DECAPODA, POTAMONAUTIDAE) FROM 2 WESTERN-CAPE RIVERS, SOUTH-AFRICA

Patterns of genetic and morphometric variation amongst five population s of Potamonautes parvispina from two rivers in the Western Cape, were examined. Genetic variation at 14 loci was investigated using protein gel electrophoresis. The results showed that the populations were gen etically invariant within and between the two drainage systems. Discri minant functions analyses of seven carapace variables demonstrated reg ional differentiation between the population groups in the two drainag e systems. Other morphometric characters exhibited a significant degre e of variation within drainage systems. Morphometric data were highly variable and were discordant with the genetic data, which suggests tha t environmental factors may be responsible for the large degree of phe notypic plasticity. Results from the present study are discussed in te rms of widespread gene flow and recent population divergence.