Genetic diversity in three natural Tunisian Lamiaceae: Rosmarinus officinalis L., Lavandula multifida L. and Thymus algeriensis L. and implications for conservation

Genetic diversity and population structure of three Tunisian Lamiaceae species Rosmarinus officinalis L., Lavandula multifida L. and Thymus algeriensis L. were assessed using allozyme electrophoresis. Populations for each species were collected from different bioclimatically zones. A high genetic variation within the populations of each species was revealed. The genotypic richness of populations before their fragmentation and the high rate of outcrossing were the main contributing factors in this high variation. Differentiation among populations was substantial for each species. Only Rosmarinus officinalis showed a significant relationship between population structure and geographic distance. Differentiation between contiguous bioclimates was less important than that recorded between discontinuous ones. Intraspecific populations genetic similarity was high. The low genetic divergence between populations and their substantial structure indicate their recent fragmentation under anthropic pressures. Implications of genetic and population structure for the development of in situ and ex situ conservation strategies are discussed. Conclusions could be applied for other lamiaceae species.