Studies On Molecular Phylogeography Of Two North Temperate Aquatic Species Hippuris Vulgaris And Sparganium Stoloniferum In China

Climatic oscillations in the Quaternary have greatly affected the distribution and abundance of north temperate plants. Although numerous studies have been conducted to address this question, these studies focused on terrestrial plants, seldom on north temperate aquatic plants. China is the southern edge for north temperate plants, and also considered as important glacial refugia of north temperate plants. That exploring the distribution pattern and population dynamics of north temperate plants in China is necessary for us to comprehensively understand the effect of climatic oscillations on north temperate plants. This study examined the phylogeographic patterns in a broad geographic sampling of two north temperate aquatic plants, Hippuris vulgaris and Sparganium stoloniferum, in China by using chloroplast regions and microsatellite loci. The main results were as follows:1. In Hippuris vulgaris, most of genetic variation occurred among populations. The level of genetic diversity of single populations was low.77.8 percentage of populations consisted of only one cpDNA haplotype and 26.4 percentage of populations consisted only one genotype. The cpDNA results revealed two distinct lineages, A and B. A is restricted to Northeast China; B is distributed in Northwest China, the Qinghai-Tibet Plateau (QTP) and North and Northeast (NNE) China; and A and B diverged ca.1.36 Ma. The nSSR data revealed two genetic clusters corresponding to the two cpDNA lineages and nonreciprocal hybridization with lineage A as the maternal lineage in Northeast China. Cluster B further divided into three subclusters:I, mainly in NNE China and the northeastern border of the QTP; ?, in Northwest China and the QTP; and ?, on the QTP. ENM predicted a marked range shift on the QTP at the LGM, retreating from the platform to the northeast and southeast edges.2. In Sparganium stoloniferum, almost all of genetic variation occurred among populations. The level of genetic diversity of single populations was low.96.8 percentage of populations consisted of only one cpDNA haplotype and 54.8 percentage of populations consisted only one genotype. The cpDNA results revealed two distinct lineages, south and north. The north lineage distributed in Xinjiang and Northeast China. The populations from these two regions genetically differentiated and represented two subspecies of Sparganium stoloniferum. The south lineage distributed other areas and was divided into two sub-lineages, east and west. Hybridization between the subspecies in Xinjiang (Sparganium stoloniferum subsp. microcarpum) and south lineage was revealed by the nSSR data. Hybridization between the subgenus in Northeast China (Sparganium stoloniferum subsp. choui) and south lineage was not found, which support treating this subspecies as species.In conclusion, genetic variation of these two north temperate aquatic species, Hippuris vulgaris and Sparganium stoloniferum, mainly existed among populations. The level of genetic diversity of single populations was low and the percentage of monomorphic populations is high. These two north temperate aquatic species showed complex evolutionary history in their southern edge region in the process of their immigration, dispersal and diversification. They had multiple genetic lineages with high differentiation, obviously phylogeographic pattern, and separate glacial refugia in China. Hybridization between different genetic lineages occurred in their contact areas, Northeast China or Northwest China. Northeast China was not only important refugia, but also the center of genetic diversity.