Genetic diversity and chemical polymorphism of Tunisian Lavandula multifida L. (Lamiaceae) populations

Eleven Tunisian natural populations of Lavandula multifida L., from different geographic regions and bioclimates, were assessed for their variability using six polymorphic loci and 35 terpenoids. Isozymes were revealed by 13% gel electrophoresis. Volatiles were analysed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). A high genetic diversity within populations and within ecological groups was revealed by allozymes as a result of both of the outbreeding system of the species and the large size of populations before fragmentation. Cluster constructed using Nei’s genetic distances showed high differentiation between populations. Those belonging to the same bioclimatic zone were not strictly grouped together. Essential oil composition varied among populations. Carvacrol (21.14 to 47.02%), acrylic acid dodecanyl ester (8.96 to 14.06%) and β-Bisabolene (12.96 to 19%) were the main components. Chemical population’s structure, at the ecological group level, based on terpenoids was concordant with that of isozymes. Matrices of Wright’s FST and Euclidean distances were also correlated. Population differentiation performed on combined data yielded similar to that shown using each marker separately. Conservation strategies should take into account the levels of genetic diversity and chemical variation in relation to population and bioclimate.