Distribution of genetic variability in southern populations of Scots pine (Pinus sylvestris L.) from the Alps to the Apennines.

Alpine and Northern Apennine populations of Pinus sylvestris L. collected from 8 different Italian sites were analysed by mitochondrial nadI intron and InterSimple Sequence Repeat (ISSR) markers, in order to describe the natural level of genetic variability and to clarify their genetic relationships. The small Northern Apennine populations are the southernmost populations of this conifer in Italy. All the analysed populations were spontaneous and reforested areas were excluded. The analysis of the polymorphisms in the nad 1 intron sequence confirmed that the Italian P. sylvestris populations have the same mitotype (mitotype a) as the Central European ones. In the genomic ISSR analysis the proportion of shared alleles between the individuals showed the highest degree of differentiation between French and Italian populations and a divergence between the Alpine and Apennine populations. Alpine populations showed a higher genetic variability (GD 0,310 ± 0,0252) than Apennine samples (GD 0,217 ± 0,019). In addition, the individuals from the Apennines did not show a clear population structure, suggesting a common genetic constitution of the Apennine P. sylvestris. It is likely that this constitution is the result of a progressively genetic isolation between the Alpine and the Northern Apennine populations from the early Holocene. The genetic constitution of the Northern Apennine populations suggests the opportunity of a management where in situ conservation of such small populations could be coupled to their use as sources of suitable local reforesting materials.