Competition between Moina macrocopa and Ceriodaphnia dubia: a Life Table Demography Study

We analyzed the effect of competition on survival- and reproduction-related parameters under two (0.5.10 6 and 1.5.10 6 cells ml -1 of Chlorella) food densities between Moina macrocopa and Ceriodaphnia dubia using the life table demography approach. In general, regardless of the presence of Moina, the average lifespan and generation time were higher for C. dubia. However, rate of population increase (r) and values of reproductive effort were higher for M. macrocopa. The net reproductive values of C. dubia grown alone varied from 7.6 to 36.6 offspring female 1 lifetime -1 , depending on Chlorella density. Corresponding values for Moina varied little (16.4 and 17.4 offspring female -1 lifetime -1 ) Values of gross reproductive rate, net reproductive rate and the generation time of both cladoceran species were higher in mixed cultures than when grown alone. The negative effect of competition was evident for both the cladoceran species, not in their reproductive rates, but in their generation times, and thus population growth rates. The role of competition and facilitation occurring between the two species was discussed in relation to different algal food levels.