Seasonal Variation Of Genetic Diversity Of Daphnia Galeata In A Tropical And Subtropical Reservoir, Southern China

Daphnia galeata is the only common daphniids in tropical and subtropical reservoirs in Its population seems to be able to over summer under strong predation pressure of in tropical and subtropical zones. Resting hatching and over summering make its population genetics be more complicated. We chose the microsatellite DNA as the neutral molecular marker to detect seasonal variation of the active populations in large and deep reservoir: Liuxihe reservoir, and analyzed how the over-summering and dormant populations do contribute to the genetic structure.We samples individuals of Daphnia galeata for continuous four years(2012-2015) and obtained twenty-five active populations, and sequence with 9 SSR locis.We found the genetic diversity ranged from 0.306 to 0.546, in which the population of 2013-Feb-1 was the lowest, and the population 2013-May was the highest. The new individuals reproduced by amictic parthenogenesis, forming all-female clonal lineages, and faced the strong strength of clonal selection, which led all locus significant deviated from Hardy-Weinberg equilibrium.The genetic structure of twenty-five populations of Daphnia galeatawas was divided into four unique groups by the analysis of the software Structure, where the highest peak was for K=4. The difference of genetic structure among groups was much higher than that within groups. The MLG diversity varied not so much among populations, and the shared MLG appeared within one year and between years. That is to say, the over-summering population existed and maintained the active population genetic diversity, but the amount of the shared MLG is very low. In the beginning of the growing season for the second year, the frequency of genotypes changed significantly, and was distinct from the last year. And there were a few shared MLG: two for 2012 and 2013, two for 2013 and 2014, and three for 2014 and 2015.In the begin of growing season, the gene flow from the egg bank contributed to the genetic diversity and genetic structure, and the over-summering populations as the only active population in the summer, which can be detected by the MLG of microsatellite DNA maker. From the MLG diversity and He decline in clonal diversity, we can conclude that the latter of clonal erosion doesn’t exist in tropical and subtropical reservoirs, but the strong clonal selection results in the seasonal change in the genetic diversity of Daphnia galeata population.