Strong genetic differentiation of the East-Himalayan Megacodon stylophorus (Gentianaceae) detected by Inter-Simple Sequence Repeats (ISSR)

Megacodon stylophorus (Clarke) Smith is a perennial alpine herb endemic to the species-rich eastern Himalayan region. Its populations are locally scattered as isolated patches throughout this region. Genetic variation within and among six populations of this species was assessed using ISSR fingerprinting with 13 primers. High levels of genetic diversity exist within species (P = 69.83%, H _T = 0.1949 and H _sp = 0.3047), while the within-population diversity is low (P = 11.21%, H _E = 0.0532 and H _pop = 0.0792). Extraordinarily high levels of genetic differentiation were detected among populations based on various statistics, including Nei's genetic diversity analysis (72.7%), Shannon's diversity index (74.01%) and AMOVA (80.70%). That is, populations shared low levels of genetic identity (I = 0.8203 ± 0.0430). This genetic structure was probably due to severe genetic drift of the small-sized patchy populations resulting from postglacial habitat fragmentations. The observed genetic structure of the populations implies that as many populations as possible should be considered for any in situ and ex situ conservation practice on this species.