Water temperature and chlorophyll a density drive the genetic and epigenetic variation of Vallisneria natans across a subtropical freshwater lake.

Plant genetic diversity differs in habitat's oscillations, especially species distributed under heterogeneous environmental conditions. Freshwater ecosystems are vulnerable to biotic and abiotic impacts, which affect the genetic and epigenetic variations in aquatic plants. The extent of environmental heterogeneous attributes can be examined based on genetic and epigenetic variations. Such variations under environmental gradient can provide evidence for understanding the correlations between rapid environmental changes and species evolution. In this study, we performed amplified fragment polymorphism length and methylated-sensitive amplified polymorphism analysis to depict the genetic and epigenetic variations of Vallisneria natans in a subtropical lake. Results showed that this species maintained a relatively high genetic diversity (mean H (E) = 0.320, I = 0.474, PPL = 85.93%) and epigenetic variation (mean eH (E) = 0.282, eI = 0.428, ePPL = 83.91%). Water body temperature and chlorophyll a density were positively correlated to the genetic and epigenetic variations. The clonal generates of V. natans depicted a relative high methylation level and shew ancestral scenario between the genet and the second clonal generation. These findings revealed that species diversity is unevenly distributed under environmental heterogeneity, even at a fine geographic scale. Environmental characteristics in relation to temperature and chlorophyll a should be considered in the analysis of the genetic and epigenetic variations. Additionally, epigenetic variations between genets and ramets should be considered with caution when applied to analysis of other aquatic species.