Genetic diversity and structure of Sinopodophyllum hexandrum (Royle) Ying in the Qinling Mountains, China

Abstract

Sinopodophyllum hexandrum is an important medicinal plant whose genetic diversity must be conserved because it is endangered. The Qinling Mts. are a S. hexandrum distribution area that has unique environmental features that highly affect the evolution of the species. To provide the reference data for evolutionary and conservation studies, the genetic diversity and population structure of S. hexandrum in its overall natural distribution areas in the Qinling Mts. were investigated through inter-simple sequence repeats analysis of 32 natural populations. The 11 selected primers generated a total of 135 polymorphic bands. S. hexandrum genetic diversity was low within populations (average He = 0.0621), but higher at the species level (He = 0.1434). Clear structure and high genetic differentiation among populations were detected by using the unweighted pair group method for arithmetic averages, principle coordinate analysis and Bayesian clustering. The clustering approaches supported a division of the 32 populations into three major groups, for which analysis of molecular variance confirmed significant variation (63.27%) among populations. The genetic differentiation may have been attributed to the limited gene flow (Nm = 0.3587) in the species. Isolation by distance among populations was determined by comparing genetic distance versus geographic distance by using the Mantel test. Result was insignificant (r = 0.212, P = 0.287) at 0.05, showing that their spatial pattern and geographic locations are not correlated. Given the low within-population genetic diversity, high differentiation among populations and the increasing anthropogenic pressure on the species, in situ conservation measures were recommended to preserve S. hexandrum in Qinling Mts., and other populations must be sampled to retain as much genetic diversity of the species to achieve ex situ preservation as a supplement to in situ conservation.

Figure 1. Locations of the 32 S. hexandrum populations in Qinling Mts. sampled for this study.

Figure 2. UPGMA clustering of S. hexandrum populations in Qinling Mts.

Figure 3. Distribution of individuals of the 32 S. hexandrum populations from Qinling Mts., according to the first (PCo1) and second (PCo2) principal coordinates.

PCo1 and PCo2 account for 13.6 and 8.7% of the total variation, respectively.

Figure 4. Mantel regression of the pairwise relationship between genetic and geographical distances for S. hexandrum populations.

Figure 5. The probable K value estimated by likelihood of the probability of data L(K) and ad hoc quantity ΔK.

Figure 6. Bayesian clustering for infering population structure of S. hexandrum populations from Qinling Mts.