Genetic variation within and among fragmented populations of endangered medicinal plant, Withania coagulans (Solanaceae) from Pakistan and its implications for conservation

Withania coagulans is an under-utilized, endangered medicinal plant that can be found scarcely as fragmented populations in South Asia. Theoretically, the fragmented population should show lowdiversity within population and higher diversity among population with low rate of gene flow. To test this hypothesis, we conducted diversity analysis of 7 populations of W. coagulans from the districts of Kohatand Karak in NWFP (North West Frontier Province), Pakistan using PBA (P450 based analogue) markers. Our results showed contrary findings from the hypothesis for fragmented population. The findingsshowed higher diversity within population and lower diversity among population like larger unfragmented populations even though the population size was less than 100 in all populations. Percentage of polymorphic bands (PPB) in these populations was 50 to 71.95% with gene diversity (H) of 0.192 to 0.298. AMOVA (Analysis of molecular variance) test showed that there was low genetic diversityamong populations (17%) and high genetic diversity within population (83%). FST value showed low genetic differentiation (0.0911) and high gene flow (Nm 2.494) among populations. Isolation by DistanceModel revealed no correlation between genetic and geographic distances as well as ecotypes (soil variation) vs genetic distances. Presumably, the larger fragments, formed long time ago due to geological changes, were reduced into smaller fragments recently due to the human pressure. the fruits of the plant are exploited for commercial purposes and the whole plant is used as fodder and fuelwood thus threatening the current survival of the limited fragmented populations. Conservation measures for the species existence are also discussed and recommended