Genetic and epigenetic variation of Trapa bispinosa under slope gradient: A case study in a subtropical freshwater lake

Dynamic environmental factors can influence the genetic diversity and epigenetic variation of aquatic plants, thus accelerate the rate of species adaptations. Trapa bispinosa is an aquatic crop which is widely distributed in China and worldwide, yet little is known about the genetic and epigenetic variations of T. bispinosa in fishery and nature habitats. By using AFLP and MSAP, we analyzed the genetic and epigenetic variations of 27 T. bispinasa populations in a subtropical freshwater lake. A relative high level of genetic diversity (mean HE = 0.312, I = 0.480, PPL = 54.90%) and epigenetic variation (mean eHE = 0.351, eI = 0.531, ePPL = 67.84%) were detected. Besides, fishery habitats maintained relative higher epigenetic variations of T. bispinosa (HE = 0.254, eI = 0.378, ePPL = 68.28%) than nature habitats (eHE = 0.253, eI = 0.376, ePPL = 67.77%). Overall variations were basically distributed within populations (ØST = 0.260, P < 0.001). Bayesian analysis revealed a pattern of genetic structure consisting of two clusters among the populations. The Mantel regression of genetic and epigenetic variation against geographic distance did not reveal any correlations, but showed a correlative relationship with environmental variables (r = −0.47, P < 0.05). Specially, genetic diversity of T. bispinosa showed a positive correlation with slope aspect. These results indicated that habitat slope may shape the pattern of genetic variation in T. bispinosa, which further illustrated that even in a fine geographical scale, genetic diversity was unevenly distributed, restoration measurements for this aquatic crop should carefully take the habitat slope into account.