Genetic diversity of Lavandula multifida L. (Lamiaceae) in Tunisia: implication for conservation

The genetic variation within and among eight Tunisian natural populations of Lavandula multifida L. , from different bioclimatic zones was assessed using random amplified polymorphic DNA (RAPDs). Of a total of 97 generated bands from seven selected primers, 84 bands were polymorphic. The genetic diversity within a population was high and varied according to the populations (0.308 < H’ < 0.459) without relationships to altitudes or pluviothermic indices of sites. The genetic differentiation among populations was high (GST = 0.395 and ΦST = 0.318). All population pairs were significantly differentiated. Among populations, within ecological groups genetic structure was high (0.219); whilst among them it was low (ΦCT = 0.049; P < 0.05). The correlation between ΦST and geographic distance matrices among pairs of populations was not significant, suggesting that genetic connectivity between populations has a stochastic component at all spatial scales. The neighbour-joining cluster analysis showed that individuals from each population clustered together. UPGMA cluster analysis showed that population groupings are not strictly in accordance with bioclimates or geographic location. The genetic differentiation in L. multifida could have occurred at local scales because of genetic drift. Efforts should be made to protect all populations. The maintenance of substantial population size should be initiated via fencing and controlling collection to restore the regeneration of populations. Resume La variation genetique au sein de et entre huit populations naturelles de Lavandula multifida L. venant de differentes zones bioclimatiques, en Tunisie, a eteevaluee en utilisant la RAPD (Random Amplified Polymorphic DNA). Sur un total de 97 bandes generees a partir de sept primers selectionnes, 84 etaient polymorphiques. La diversite genetique etait elevee au sein d’une population et variait selon les populations (0,308 < H’ < 0,459), sans lien avec l’altitude ou les indices pluvio-thermiques des sites. La differenciation genetique parmi les populations etait elevee (GST = 0.395 et ΦST = 0.318). Toutes les paires de populations etaient significativement differenciees. Parmi les populations, dans les groupes ecologiques, la structure genetique etait elevee (0,219) tandis qu’entre eux, elle etait faible (ΦCT = 0.049; P < 0.05). La correlation entre ΦST et les matrices de distances geographiques entre paires de populations n’etait pas significative, ce qui suggere que la connectivite genetique entre populations a une composante stochastique a toutes les echelles spatiales. L’analyse neighbour-joining-de groupe a montre que des individus de chaque population se regroupent ensemble. Le groupe d’analyses par la methode UPGMA a montre que des regroupements de populations n’etaient pas strictement lies a un bioclimat ou a une situation geographique. La differentiation genetique de L. multifida pourrait s’etre faite localement en raison de la derive genetique. Il faudrait faire des efforts pour proteger toutes les populations. La conservation de populations de taille importante devrait etre lancee en posant des clotures et en controlant les collectes afin de relancer la regeneration des populations.