The evolution of mitochondrial dna in partula

The mitochondrial DNA of species of land snails of the genus Partula from the Society Islands has been analysed by means of restriction enzymes to determine relationships within the genus.Seventeen variable restriction sites were mapped onto the 14.5 kb mtDNA. These sites are highlyvariable within species. In P. suturalis, those genotypes occurring within a population are usuallyseparated by single-step changes, and the differences between populations are geographicallycoherent. There is no detectable association between the distribution of mitochondrial genotypesand the occurrence of dextral or sinistral populations, confirming that chirality does not constitute agenetic barrier in this species. P. taeniata also shows a coherent geographic pattern of genotypedistribution within and between populations. The mitochondrial differences between morphologically similar populations in the northeast and northwest suggest that the similarity may be the resultof convergence. Despite the regular patterns of distribution within species, some genotypes arewidely shared among species. One pattern was found in four species on Moorea and two species onthe neighbouring island of Tahiti. Shared genotypes may represent ancestral forms or they may haveresulted from hybridization. However we believe that the most attractive hypothesis is that they aresubject to selection. Studies of Partula demonstrate that the evolution of the morphological, electrophoretic, and mitochondrial phenotypes occur at variable rates, independently of one another.