Allozyme variation amongst populations of the freshwater crab, Potamonautes perlatus (Decapoda: Potamonautidae) in the Berg River system, Western Cape

Abstract

The Cape river crab, Potamonautes perlatus, is widely distributed in streams and rivers of the Western Cape where it exhibits considerable morphological variation. Recent genetic work on populations in the Olifants River system has demonstrated the existence of a new cryptic species of river crab, while populations of P. perlatus in the nearby Berg River system remained uninvestigated. Six populations of P. perlatus  were collected from along the length of the Berg River system (125 km) and the genetic structure was investigated using allozyme electrophoresis. Results from 14 allozyme loci showed that the populations were genetically invariant across the river system. It is suggested that gene flow may be responsible for the poor genetic differentiation amongst populations in the Berg River system. The implication for future management of the system is briefly discussed.