Spatial Variation of Sexual Reproduction in the Remnant Population of the Endangered Species Myricaria laxiflora

Abstract:The construction of the Three Gorges-Gezhouba cascade water conservancy and hydropower project has changed the fluctuation pattern of river water-level downstream the dams. The spatial heterogeneity of sexual reproduction in the remnant population of the endangered species Myricaria laxiflora was uncovered by investigating the changes of flowering and fruiting traits in the population along fluctuation gradient at Guanzhou island, Zhijiang city. The impact of the construction of the cascade water conservancy and hydropower project on the sexual reproduction of remnant populations was analyzed based on the characteristics of water-level fluctuation rhythm in the habitat of M. laxiflora. The results showed that there were significant differences in the sexual reproduction of the remaining population among different fluctuation gradients. The flower branch number per plant, flower number per branch and flower number per plant of plants at the upper part of the fluctuation zone was 66.09%, 50.14% and 98.63% higher than those at the middle part, and 79.50%, 283.33% and 461.05% higher than those at the lower part, respectively. The fruit branch number per plant, fruit number per branch, fruit number per plant, seed number per fruit and seed germination percentage of plants at the upper part of the fluctuation zone were 60.17%, 25.26%, 88.05%, 6.96% and 30.69% higher than those at the middle part, and 97.39%, 82.45%, 208.31%, 19.12% and 45.91% higher than those at the lower part. The correlation analysis showed that there were significant correlations between the flowering and fruiting characteristics and fluctuation gradient, plant exposing period, soil water content and temperature. The influence of environmental factors on sexual reproduction was in the order of exposing time, fluctuation gradient, daily average temperature and soil moisture content. The regulation of the cascade water conservancy and hydropower projects upstream for flood control and power generation results in a delay in exposure time and a sharp decrease in water level at the habitat. The resulting decrease in temperature and soil moisture during the flowering and fruiting period would impact the sexual reproduction of the remaining population.