Appendix
Appendix: 1
Pilot experiment.
We chose 3 species with different habitat specialization (Daphnia, Ceriodaphnia and Potamocypris sp.) except for Nitocra spinipes. Generally, N. spinipes is the most common and abundant harpacticoid copepod species found in the Jamaican rock pool system - the source of the species (see Pandit et al. 2009). N. spinipes tolerates brackish water well (0.5 to 30 ppt of salinity).
Like other three species, this species has also high reproductive output and short generation time (Bengtsson 1978).
We first assessed population dynamics of the three species at different salinities. We reared them separately in media with different salinity concentrations (0, 2, 4 and 6ppt) over 3 weeks (June 3-June 24), to determine levels of salinity suitable for creating effective yet non-destructive amplitude of environmental fluctuations. Because generation times of these species are short, the pilot project provided information about their population necessary for the design of the main experiment. A total of 12 microcosms (4 salinity levels × 3 replications) were set up for each species to a total of 36 experimental microcosms. Initially, fifty individuals of each species were placed in each experimental microcosm. Sampling started 2 days after the beginning of the experiment by gently stirring water with a glass stirrer, followed by taking three aliquots of 50mL from each experimental microcosm at two day intervals. The organisms were counted using a dissecting microscope and then returned unharmed to their respective experimental microcosms. Every seven days, the medium of each microcosm was replaced with fresh medium of same salinity (after enumeration only). 50 ml water with algae at concentration of 1.5 x 106 cells/ml as food were added along with the new medium. There were also some dead particles in the solution of algae, but we did not count them assuming that variation of the concentration of the dead particles in the solution was not significantly different from week to week.
Figure A1. Changes in population abundance of Ceriodaphnia, Daphnia and Potamocypris under different salt concentrations (symbols legend in the right panel) during the pilot experiment. Points are the mean ± 1 standard error based on three replicates.
The individuals of Ceriodaphnia and Daphnia survived in the salt concentration of 6 ppt, but their density decreased at that salinity levelto the point that population ofCeriodaphnia disappeared after 14 days. In contrast, the density of Potamocypris did not change in elevated salinity of 6 ppt. Thus, we defined Potamocypris as a generalist, Ceriodaphnia as a specialist and Daphnia as a species with an intermediate degree of salinity tolerance or specialization.
Appendix: 2
Experimental Design
Figure A2. Experimental design: D, C, P, and N represent Daphnia, Ceriodaphnia., Potamocypris and Nitocra spinipes (a harpacticoid) respectively. Squares represent microcosms, and each cluster of 4 microcosms is a metacommunity. Circles within the microcosms represent species and each shading pattern represents a different species. One, two, three, and four shading patterns represent one, two, three, or four species, respectively. Similarly, size of the circle represents the initial number of introduced individuals of each species. The largest size represents 100 individuals and the smallest size 25 individuals.
Appendix: 3
Fig. A3. Changes in population densities through the course of the main experiment for three species and 5 different species combinations (shown in respective legends) in three different EF treatments (Control, Low and High). The points are the averaged population size of each metacommunity ± standard error based on fourcommunities in each treatment for each species combination scenario.
Appendix: 4
Table A4.Multiple comparison of population synchrony using a post-hoc student -Benjamini-Hochberg “BH” test where table 3.a) theeffect ofEF; table 3.b) the effect of species richness. These value are the p -difference of the population synchony between groups.
Table A4.a:
Species / EF treatment / Control / Low / HighCeriodaphnia / Control
Low / 0.341
High / 0.057 / 0.167
Daphnia / Control
Low / 1
High / 0.05 / 0.05
Potamocypris / Control
Low / 0.960
High / 0.960 / 0.960
Table A4.b
Species / Species richness / s1 / s2 / s3 / s4Ceriodaphnia / S1
S2 / 0.103
S3 / 0.069 / 0.389
S4 / 0.028 / 0.103 / 0.389
Daphnia / S1
S2 / 0.083
S3 / 0.083 / 0.764
S4 / 0.019 / 0.083 / 0.159
Potamocypris / S1
S2 / 0.030
S3 / 0.000 / 0.000
S4 / 0.000 / 0.001 / 0.621
Appendix: 5
Table A5a: ANOVA table for the difference in growth rates of the three species in control and monoculture treatment. Here we used the growth rate of each species of their monoculture treatment (D, C, P) in control EF treatment and compared their growth rates to determine whether they differed among the three species.
Effect / SS / Df / MS / F / pSpecies / 0.015 / 2 / 0.007 / 1.692 / 0.237
Error / 0.041 / 9 / 0.004
Table A5b: ANOVA table for the difference in growth rate and density of Ceriodaphnia in the metacommunities with Daphnia (the metacommunity containing Ceriodpahnia and Daphnia) and with out Daphnia (the metacommunity containing Ceriodaphnia and Potamocypris)..
Parameter / Effect / SS / Df / MS / F / pGrowth rate / Combination / 0.03 / 1.00 / 0.03 / 0.49 / 0.51
Error / 0.40 / 6.00 / 0.07
Density / Combination / 796.67 / 1.00 / 796.67 / 446.09 / 0.00
Error / 10.72 / 6.00 / 1.79
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