GENETIC DIVERGENCE AND BIOGEOGRAPHY OF NATURAL POPULATIONS OF Macrobrachium rosenbergii

Abstract

ABSTRACTElectrophoretic studies of gene‐enzyme variation in natural populations of the freshwater prawn (Macrobrachium rosenbergii) are undertaken to quantify the amount of racial divergence among geographically separated natural populations. A total of 440 individuals from 11 localities spread from Sri Lanka to New Guinea, Palau and the Hawaiian cultured stocks are analyzed for genetic variation in as many as 31 electrophoretically detectable proteins. Within‐population variability is relatively low: the average proportion of heterozygous loci in any given individual is 2.8% and the average proportion of polymorphic geneenzymes per population is 14%.Population differences are summarized by proportions of loci having no genotypes in common between populations (“% diagnostic loci”). Prawn populations from Australia, New Guinea, the Philippines, and Palau are well differentiated from the rest, with genetically fixed enzyme differences at over 20% of the gene‐enzyme systems. That this major discontinuity in the gene pool of M. rosenbergii corresponds to the well recognized zoogeographic boundary known as Wallace' Line suggests that insular distribution has contributed to genetic divergence.One or 2 fixed or nearly fixed differences were also found among populations within the 2 major races east and west of Wallace' Line. These results support the hypothesis that this species has undergone substantial racial divergence over its range and that natural populations represent a tremendously diverse genetic resource for freshwater prawn aquaculture.