Abstract
RFLP of chloroplast DNA was studied in two diploid and five tetraploid populations of Lotus alpinus (D.C) Schleicher in the French Alps. This was compared with four non alpine populations and two cultivars of Lotus corniculatus L. (24x) introduced in the alpine valley. Based on the 13 sites and 11 lenght mutations detected, seven distinct haplotypes could be identified, which clustered in two groups, corresponding to the two Lotus species. With only one exception, the diploid and the tetraploid L. alpinus plants had the same haplotype. This is to be expected because morphological variation and tetrasomic inheritance suggest that the tetraploid were derived from the diploids by autotetraploidy. In L. corniculatus two very similar haplotypes were found in the natural very distant populations. In contrast the chloroplast DNA haplotypes of the two cultivars differed considerably from each other and were more related to those observed in L. alpinus, suggesting that these cultivars may derived maternally from L. alpinus individuals. In one tetraploid L. alpinus population, a single cp DNA haplotype was identified. As this halplotype was related to those observed in the L. corniculatus groupe, local genetic introgression may have occured between 4x L. alpinus plants and cutivated L. corniculatus.