Essential oil variation among natural populations of Lavandula multifida L. (Lamiaceae).

Volatiles from twelve wild Tunisian populations of Lavandula multifida L. growing in different bioclimatic zones were assessed by GC (RI) and GC/MS. Thirty-six constituents, representing 83.48% of the total oil were identified. The major components at the species level were carvacrol (31.81%), beta-bisabolene (14.89%), and acrylic acid dodecyl ester (11.43%). These volatiles, together with alpha-pinene, were also the main compounds discriminating the populations. According to these dominant compounds, one chemotype was revealed, a carvacrol/beta-bisabolene/acrylic acid dodecyl ester chemotype. However, a significant variation among the populations was observed for the majority of the constituents. A high chemical-population structure, estimated both by principal component analysis (PCA) and unweighted pair group method with averaging (UPGMA) cluster analysis based on Euclidean distances, was observed. Both methods allowed separation of the populations in three groups defined rather by minor than by major compounds. The population groups were not strictly concordant with their bioclimatic or geographic location. Conservation strategies should concern all populations, because of their low size and their high level of destruction. Populations exhibiting particular compounds other than the major ones should be protected first.