Genetic variability of relict Rhododendron ferrugineum L. populations in the Northern Apennines with some inferences for a conservation strategy

In this study, the genetic diversity of three Rhododendron ferrugineum L Apennine populations (AP1, AP2, and AP3) was analyzed and compared to three populations of the Maritime Alps and six populations of Central-Eastern Alps. Genetic variations across microsatellite markers revealed that the Apennine populations show some clonal individuals and the lowest genetic diversity values (AP1 and AP3 A([18]) values are 2.46 and 2.31, respectively), as well as heterozygosity deficiency with respect to the Alpine populations. Genetic relationships among populations (Nei's genetic distance) showed that populations from the Central-Eastern Alps and from the Maritime Alps clustered in two separate groups. Unweighted pair group method with arithmetic averages as well as PCA analysis showed a clear separation of the three Apennine populations according to the high FST values detected (AP1-AP2 = 0.427; AP1-AP3 = 0.446; AP2-AP3 = 0.325). Mantel test revealed a significant correlation between genetic and geographical distance matrices (r = 0.314, P = 0.001, 999 permutations). Concerning the relationship between Apennines and alpine population, PCA analysis showed a clear genetic similarity among Maritime Alps populations and individuals of AP1 population. Considering the geographical and ecological peripheral condition of these populations and the high impact of the climatic changes on their habitat, we suggest the combination of in situ and ex situ conservation strategies to preserve the genetic diversity of this species in the Northern Apennines.