Genetic differences between continuous and disjunct populations: Some insights from sal (Shorea robusta Roxb.) in Nepal

摘要

Sal (Shorea robusta Gaertn., Dipterocarpaceae) is a wind-pollinated tropical tree species found in southern Asia. We investigated the genetic diversity and structure at four microsatellites of 15 populations comprising continuous-peripheral and disjunct-peripheral populations in Nepal. Estimates of genetic diversity (N_A = 8. 98, H_O = 0. 62, H_E = 0. 69) were similar when compared with those of other tropical tree species. A higher level of genetic diversity was observed in continuous-peripheral populations (N_A = 9. 61, H_O = 0. 67, H_E = 0. 72) as compared to disjunct-peripheral (N_A = 8. 04, H_O = 0. 55, H_E = 0. 64). Population differentiation was higher among disjunct-peripheral populations (F_(ST) = 0. 043) than among continuous peripherals (F_(ST) = 0. 012). There was a significant association between gene flow distances and genetic differentiation (r~2 = 0. 128, P ≤ 0. 007). No spatial arrangement of populations according to their geographical locations was found. Based on observed genetic diversity protection of some populations in continuous-peripheral range are suggested for the sustainable conservation of genetic resources of the species while protection of some disjunct-peripheral populations are also recommended for conserving rare alleles.