AN EVALUATION OF RANDOM AMPLIFIED POLYMORPHIC DNA (RAPD) FOR THE IDENTIFICATION AND PHYLOGENY OF FRESH-WATER SNAILS OF THE GENUS BULINUS (GASTROPODA, PLANORBIDAE)

The Random Amplified Polymorphic DNA (RAPD) assay was used to study ge netic variation within and between 9 species of the genus Bulinus and to determine whether RAPD profiles could be used as markers for identi fication purposes. RAPDs were generated with 8 primers of two differen t sizes (10mers & 15mers) and were visualised using both polyacrylamid e gel electrophoresis (PAGE) with silver staining and agarose gel elec trophoresis with ethidium bromide staining. The species groups of Buli nus had few similarities in their RAPD profiles and there was interspe cific variation within groups. Intrapopulation variation was observed, with all primers, for B. globosus collected from a single site in Zim babwe. PAGE/silver staining methods visualised a greater number of RAP Ds in comparison with agarose/ethidium bromide methods. Phenetic analy sis indicated that distance estimates between taxa were sometimes non- additive and the phylogenetic analysis of such non-metric data is disc ussed. The resultant phenograms, constructed using a least squares met hod, were constrained almost into a polytomy with topologies often dif fering between data sets. It was concluded that this phenomenon was mo st likely attributable to large nucleotide divergences between the spe cies groups which go beyond the phylogenetic scope of RAPD analysis. R APD profiles, when used in conjunction with other taxonomic methods, m ay contribute to the identification of species of Bulinus on a regiona l basis, but the observed variability in a natural population suggests that a diagnostic RAPD profile for each species throughout its geogra phic range is unlikely.