Genetic variation and structure in endangered populations ofSphagnum palustreL. in Italy: a molecular approach to evaluate threats and survival ability

The conservation status of endangered Italian populations of the peatmoss Sphagnum palustre L. was evaluated through the study of their intraspecific genetic variation and structure. One-hundred-thirty-eight shoots from four populations were analyzed by 35 inter-simple sequence repeat (ISSR) loci. Molecular diversity indices highlight a general low level of variation, which is higher in centre-northern populations than in the southernmost one. AMOVA indicates that most variation is partitioned among populations, supporting a low level of gene flow and a severe isolation among them (FST = 0.7071–0.9198; Nm = 0.106). Mantel test gave a significant correlation (0.8634, P = 0.0083) between genetic and geographical distances. A strong association among loci suggests that recombination due to sexual reproduction contributes poorly to genetic variation observed, supported by the lack of sporophytes in the study areas. Both experimental results and theoretical predictions suggest a concrete risk of local extinction for the studied populations, further increased by fragile habitats hosting the species in Italy. The southernmost population is the most threatened, due to combined effects of lower genetic variation and geographic isolation.