Comparison of the genetic diversity in two species of cycads

Inter-simple sequence repeat (ISSR) markers were used to examine the level and distribution of genetic diversity in two cycad species: Cycas parvula S. L. Yang and C. balansae Warburg. The former is found in only two adjacent populations and the latter in a relatively wider distribution. Although genetic diversity in C. balansae (H-e = 0.1301) is higher than that in C. parvula (H-e = 0.0538), both are still low in comparison with the mean value (H-e = 0.169) in gymnosperms. This confirms the general opinion that cycads are genetic relics. The genetic differentiation in both species, however, presents a striking contrast: G(st) is 0.0978 in C. parvula, but 0.4003 in C. balansae, which may be ascribed to the difference in distances between their populations.