Genetic Diversity And Spatial Genetic Structure In Scirpus Mariqueter (Cyperaceae)

Wetland is of extremely high biodiversity, and is one of the most productive ecosystems in the world. Like other ecosystems in the world, the continuing loss of biodiversity is threatening the ecosystem function and structure of this ecosystem. Biological invasion can deeply suppress the indigenous species, and thus becomes an important factor influencing local biodiversity. Revealing the spatial genetic variation and gene dispersal patterns provides an essential background for the restoration of indigenous species. Therefore, it is necessary to carry out population genetic study for the conservation strategy of the endangered species in wetland ecosystems.Here, we focused on a saltmarsh plant, Scirpus mariqueter, which is unique in china, mainly growing in the intertidal zones from the Yangtze River estuary to the Hangzhou Bay. However, due to invasion from Spartina alterniflora Loisel. and human activities, the present population size of remaining S. mariquter populations has been greatly reduced in the recent several decades.To protect the coastal wetland ecosystem and recover the damaged populations, 14 populations were analyzed using microsatellite to assess the genetic diversity within each population, and to evaluate the relationships among them and determining their genetic structure. Conservation actions based on the genetic knowledge are necessary to mitigate the effects of invasion and human-induced disturbances. Three main conclusions are as follows:All populations experienced historical bottleneck events, which may have a combined effect of changing reproduction mode and microhabitat heterogeneity, leading to the low level of intra-population genetic diversity regardless of strong inter-population gene flow.Significant spatial genetic structure was detected within 6m using spatial autocorrelation analysis. The heterogeneity test for fine-scale genetic structure between ramet-level and genet-level within TJ population showed that the clonality of this species is weak because the dispersal variance of sexual reproduction was much larger than vegetative reproduction dispersal, suggesting that clone growth was restricted within population and inter-population gene flow mainly depended on sexual reproduction.At large scale, we found an overall pattern of isolation by distance, in which all populations were clustered into 2 groups and the strength of gene flow decreased with increasing distance between populations. Great differentiation was found between the populations in different water systems due to isolation by distance. Gene dispersal might be facilitated by tidal wave and water flow, reducing genetic differentiation between populations, consequently contributing to the maintenance of effective population size and genetic variation.