INSTYTUT DENDROLOGII

Imen Ben El Hadj Ali, Arbi Guetat, Mohamed Boussaid

Genetic diversity of North African Thymus algeriensis in Tunisia: Population structure and implication for conservation

Dendrobiology 2012, vol. 67: 67-77

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 Abstract: The genetic diversity within and among nine natural populations of Thymus hirtus Willd. subsp. algeriensis (Boiss. et Reut.) Murb. from different geographical and bioclimatic zones were assessed using Random Amplified Polymorphic DNA data. A total of 154 bands were generated from seven selected primers. 141 bands were polymorphic (P=91.56%). The genetic diversity within a population based on Shannon's index which was high (H'_pop=0.307) and varied according to bioclimatic zones. A high genetic differentiation among populations (G_ST=0.335 and F_ST=0.296) was revealed, suggesting a population isolation and a low level of gene flow among them. The major proportion of the variation was attributable to individual differences within populations. The genetic structure is in accordance with geography distances. The Neighbour- joining tree based on Nei's and Li's genetic distance among individuals showed that individuals from each population clustered together. The UPGMA dendrogram based on F_ST values revealed three clusters each of them includes populations closuring to their geographical origin. The high genetic structure of populations resulted from genetic drift caused both by the habitat fragmentation and the low size of most populations. The in situ conservation should interest all populations. The ex situ conservation should be based on the collection of seeds rather within than among populations because of the maximum of variation was revealed within populations.

Additional key words: Genetic differentiation, molecular markers, natural populations.