Genetic variation and gene flow in Alpine diploid and tetraploid populations of Lotus (L. alpinus (D.C.) Schleicher/L. corniculatus L.). II. Insights from RFLP of chloroplast DNA

RFLP of chloroplast DNA was studied in two diploid (2x) and five tetraploid (4x) 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. (4x) introduced to the Alpine valleys. Based on the 13 site and 11 length 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 tetraploids were derived from the diploids by autopolyploidy. In L. corniculatus, two very similar haplotypes were found in the natural very distant populations. In contrast, the chloroplast DNA (cpDNA) 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 be derived maternally from L. alpinus individuals. In one tetraploid L. alpinus population, a single cpDNA haplotype was identified. As this haplotype was related to those observed in the L. corniculatus group, local genetic introgression may have occurred between 4x L. alpinus plants and cultivated L. corniculatus.