Abstract
Many aquatic plant species are distributed over large areas and diverse environments with populations interconnected by abiotic and biotic mediators. Here, we examined differences and similarities in the population genetic structure of six sympatric and widespread aquatic plant species. We sampled the aquatic species from six Chinese lakes found on plateaus, plains, and different river systems and analyzed them using inter‐simple sequence repeat (ISSR) markers. Samples originating from each lake tended to cluster together. Of the six species, only Nymphoides peltata and Myriophyllum spicatum could be divided into plateau and plain groups, once Taihu Lake individuals were excluded. Genetic similarities between populations connected by the Yangtze River were not consistently higher than unconnected populations. Populations from Taihu Lake and/or Weishanhu Lake were distant from other lake populations for all species except Potamogeton lucens. The Taihu and Weishanhu populations clustered for Ceratophyllum demersum and Typha latifolia. Hydrophilous C. demersum had the lowest gene flow (Nm = 0.913), whereas the entomophilous Hydrocharis dubia (Nm = 2.084) and N. peltata (Nm = 2.204) had the highest gene flow. The genetic relationships among distant populations of aquatic plants reflect the comprehensive effects of environmental selection pressure and biotic and abiotic connectivity. Differences in environmental factors between plateau and plain lakes and long distance hydrochory have limited importance on aquatic plant genetic structures. Among multiple evolutionary forces, gene flow mediated by birds may play the most important role in the formation of genetic patterns in the six species examined. For example, the close genetic relationship between Taihu Lake and Weishanhu Lake populations, each in different river systems and with different climates, may be related to the migration routes of birds. Differences in gene flow among the six aquatic plants may be attributable to different bird‐transport and the fruit traits of each species.
Highlights
Many aquatic plants are distributed over large areas and diverse environments and comprise populations interconnected by abiotic and biotic mediators
On the third terrain step, large differences in latitude lead to different climates on the North China Plain and plains of the middle and lower reaches of the Yangtze River. These environmental differences may result in different selection pressures on aquatic plants, different adaptations to local environments, and genetic differentiation among species inhabiting these lakes
We hypothesize that (1) population genetic differentiation could arise from divergent environmental pressures or demographic factors related to differential population sizes and isolation of lakes, whereas (2) gene flow mediated by water, fish, and birds homogenizes populations
Summary
Many aquatic plants are distributed over large areas and diverse environments and comprise populations interconnected by abiotic (e.g. water) and biotic mediators (e.g. birds; Barrat-Segretain, 1996; Lacoul & Freedman, 2006; Santamaría, 2002; Wu, Yu, Li, & Xu, 2016). Connectivity mediated by water and birds favors gene flow and tightens genetic relationships among populations (Chen, Li, Yin, Cheng, & Li, 2009; Chen, Xu, & Huang, 2007; Nilsson, Brown, Jansson, & Merritt, 2010; Pollux, Luteijn, Van Groenendael, & Ouborg, 2009; Wang, Song, Liu, Lu, & Li, 2010) Over evolutionary time, these opposite forces work interactively on widespread species inhabiting similar areas, but the question remains: how are patterns of population genetic structure for sympatric widespread plants similar?. On the third terrain step, large differences in latitude lead to different climates on the North China Plain (warm temperate monsoon climate) and plains of the middle and lower reaches of the Yangtze River (subtropical monsoon climate) These environmental differences may result in different selection pressures on aquatic plants, different adaptations to local environments, and genetic differentiation among species inhabiting these lakes. We hypothesize that (1) population genetic differentiation could arise from divergent environmental pressures or demographic factors related to differential population sizes and isolation of lakes, whereas (2) gene flow mediated by water, fish, and birds homogenizes populations
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