Genetic diversity and population structure of Tunisian Pancratium maritimum L. (Amaryllidaceae).

Pancratium maritimum (Amaryllidaceae) is mainly grown on sandy Mediterranean coasts. Populations were at present endangered and represented by scattered individuals as a result of habitats destruction and over harvesting for essential oil production. Conservation strategies firstly need the analysis of the genetic diversity of populations. The species maintains high levels of genetic diversity within populations (46.42% of polymorphic loci, and 0.137 and 0.157, respectively observed and expected heterozygosities). Substantial variation within population was observed (F ST = 0.265). The high size of populations before fragmentation and the species mating system could explain variation. Genetic divergences between populations showed populations grouping without relationship to bioclimates. A high differentiation among populations resulting from a limited gene flow was observed. The low genetic divergence among populations and their high structuring indicate their recent isolation as a result of anthropic pressures. In situ conservation strategies should take into account the ecological factors for each population. They should first interest populations with high level of polymorphism. Ex situ conservation should be based on the collection of seeds or bulbs within population rather than between populations because of their high intra population polymorphism.