Conservation genetics of an endemic from the Mediterranean Basin: high genetic differentiation but no genetic diversity loss from the last populations of the Sicilian Grape Hyacinth Leopoldia gussonei

The Mediterranean Basin is a biodiversity hotspot, housing >11.000 narrowly endemic plant species, many of which are declining due to mass tourism and agricultural intensification. To investigate the genetic resource impacts of ongoing habitat loss and degradation, we characterized the genetic variation in the last known populations of Leopoldia gussonei, a self-compatible endangered Sicilian Grape Hyacinth numbering less than 3,000 remaining individuals, using AFLP. Results demonstrated significant genome-wide genetic differentiation among all extant populations (ΦST = 0.05-0.56), and genetic clustering according to geographic location. Gene diversity was fairly constant across population (mean HE = 0.13) and was neither affected by current population size nor by spatial isolation. Vegetation analysis showed the presence of known invasive weeds in a quarter of the populations, but we found no relation between genetic diversity and plant community composition. The marked genetic differences among populations and the profusion of rare and private alleles indicate that any further population loss will lead to significant losses of genetic diversity. Conservation efforts should therefore focus on the preservation of all sites where L. gussonei still occurs, yet the deliberate introduction of diverse material into the smallest populations seems unneeded as clonality likely mitigated genetic drift effects thus far. More generally, our findings support the view that endemic plant species with a narrow ecological amplitude, as many specialists in Mediterranean coastal ecosystems, are highly genetically differentiated and that conservation of their genetic diversity requires preservation of most, if not all of their extant populations.