ENVIRONMENTAL CALCIUM, AND MITOCHONDRIAL-DNA POLYMORPHISM AMONG LOCAL-POPULATIONS OF GAMMARUS-FOSSARUM (CRUSTACEA, AMPHIPODA)

Mitochondrial DNA sequence analysis was used to investigate genetic di versity and phylogeographic population structure among geographically isolated alpine populations of the amphipod Gammarus fossarum. This st udy was performed across a region with an important glacial history an d substantial geographical variations in calcium levels, in order to e valuate the relative impact on the genetic diversity of the population history and this environmental factor known to be associated with loc al adaptation and population growth. Analysis of the nucleotide sequen ces for a 376-bp segment of the cytochrome c oxidase I gene in 84 spec imens from seven different populations revealed 20 different haplotype s distributed into five major lineages that are not geographically str uctured. Analysis of molecular variance indicates that the populations from the crystalline massif are less diverse than those living on lim estone, suggesting a global correlation between genetic diversity and calcium concentration of the water. However, the role of this environm ental factor appears to be indirect, with Smaller population size lead ing to lower genetic diversity.