HAPLOTYPE RICHNESS IN REFUGIAL AREA OF MARITIME ALPS: PHYLOGEOGRAPHICAL STRUCTURE OF SAXIFRAGA CALLOSA AND RELATIOSHIPS WITH RELATED TAXA

Resumen

Saxifraga callosa is a species spread in South-Eastern France and Italy with high diffusion in Maritime Alps. This species lives in more or less vertical limestone rocks at an altitude of between 200 and 2,000 m and it ranges from Southewestern Alps (Cottian and MaritimeAlps, Provence) through the Apuane Alps and the Apennines to southern Italy, Sardinia and Sicily (Webb & Gornall, 1989). The diffusion of the species occurs exclusively through seeds. A multiple molecular approach, using ITS, AFLP, cpDNA markers and chloroplast microsatellite (cpSSR), allowed a comprehension of the infraspecific relationships and the construction of haplotype network. By sequencing of ITS regions confirmed that the subsp. catalaunica is clearly a separate species. The application of the ‘NewHybrids’ software to AFLP data-sets recognised S. lantoscana as a natural outcross between S. callosa subsp. callosa and S. cochlearis. Genetic variability within populations was estimated by determing: i), the number of haplotypes per polymorphic population, ii), the haplotype diversity and iii), the Shannon index. Genetic structure was estimated through molecular variance analysis (AMOVA). Total genetic diversity in variance components was calculated in and out the Maritime Alps and in its north and south areal. The size variant of all tested loci amounts to 11 different haplotypes in S. callosa. A haplotype network was constructed by using chloroplast microsatellite (cpSSR).The highest number of haplotypes was found in the Maritime Alps. Analysis of the haplotype distribution showed that population subdivision across all populations was high and the existence of a strong genetic divergence between north and south areals (38%). The study of haplotypes legitimated conclusions on phylogeographical inferences across the species assortment and on the identification of a centre of diversità in the Ligurian Alps to be interpreted as a peripheral glacial refugia during the Ice Ages.