Sexual reproduction of Daphnia in a deep temperate reservoir: the phenology and genetics of male formation
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Long-term persistence of a Daphnia population is allowed by the production of dormant stages, produced mostly through sexual reproduction. We investigated the spatio-temporal dynamics of male production in a spring population of Daphnia galeata in the reservoir, and compared the genetic structure of three groups within this population: male-, female-producing females, and adult males. With a fine resolution sampling design and the use of highly variable microsatellite markers we revealed that: (1) the spring period of male offspring production was delimited in time with minimum interannual variation to about 3 weeks, and in space to the upper 5-m water layer; (2) there were no remarkable changes in the clonal composition of male-producing females within the period of male production; (3) overall certain clones exhibited a higher tendency to produce male offspring and therefore the clonal structure of male-producing lineages was significantly different from that of female-producing lineages; and (4) the clonal structure of male-producing females was not significantly different from that of adult males occurring later in the reservoir. This suggests that males were not subjected to any significant selective forces till maturity and the male-producing females confer a long-term fitness advantage over female-producing females.
KeywordsDaphnia Reservoir population Male induction Clonal structure Microsatellite
The authors thank to two anonymous reviewers for helpful comments on an earlier versions of the manuscript and D. W. Hardekopf for the linguistic revision of the text. The study was supported by Czech Science Foundation grant 206/09/1325. I. Vaníčková was also supported by the Grant Agency of the University of South Bohemia (project no. 142/2010/P) and Erasmus Programme (EU).
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