Genetic variation at chloroplast microsatellites (cpSSRs) in Abies nebrodensis (Lojac.) Mattei and three neighboring Abies species

Abies nebrodensis (Lojac.) Mattei (Sicilian fir) is an endangered species r epresented by only one population of 29 adult individuals occurring in a li mited area of the Madonie Range in northern Sicily (Italy). Taxonomic bound aries between this taxon and the neighboring Abies species are not clear. I n this study, we used six chloroplast simple-sequence repeats (cpSSRs) to i nvestigate the population genetic structure and the distribution of chlorop last haplotypic variation in A. nebrodensis and three of the neighboring Ab ies species: Abies alba (Mill.), Abies numidica (De Lann) and Abies cephalo nica (Loud.). Our aims were to quantify the level of cpDNA differentiation within the Abies populations and to shed light on the history of A. nebrode nsis. Diversity levels based on the haplotype frequency at six cpSSRs were high, especially in A. alba and A. cephalonica. In all, we found 122 haplot ypes among the 169 individuals analyzed, and the four species were distingu ished from each other by their haplotype composition. The majority of the h aplotypes (76%) were detected only once, but in A. nebrodensis seven indivi duals (41% of the sample population) shared the same haplotype. Moreover, t he seven A. nebrodensis individuals with an identical haplotype showed a te ndency to be geographically grouped within the population's limited range. The analysis of molecular variance (AMOVA) showed a significant difference in the level of apportionment of gene diversity between the species A. alba and A. cephalonica (F-ST=0.191 and 0.012, respectively). AMOVA analysis co nducted over all populations from the four species showed that 19% of the t otal cpSSR variation was attributable to differences among species, 6% was due to differences among populations within species, and 74% to differences within populations. The high percentage of unique haplotypes identified co nfirms the power of cpSSR haplotype analysis for identifying individual tre es in individual Abies populations. Our results indicate that A. nebrodensi s differs from the other three Abies species investigated and support its c lassification as an independent taxon. The results also showed a decreased level of variation in A. nebrodensis and suggested that the species has exp erienced a genetic bottleneck during the last two centuries.