Better understanding the cause and processes of population synchrony is an important issue for population management. However, the number and traits of coexisting species on population synchrony have not been tested although they influence population dynamics. We report on an experimental investigation of the synchronizing effects of environmental variability on focal species, Daphnia magna, Ceriodaphnia sp. and Potamocypris sp., in microcosms of varying invertebrate richness (1-4). We introduced environmental variation by alternating addition of salt and distilled water into the culture media. Two species (Daphnia magna, Ceriodaphnia sp.) have lower salinity tolerance while Potamocypris sp. has high salinity tolerance.

Results/Conclusions:

We found that population synchrony of both Daphnia magna and Ceriodaphnia was significantly different among the microcosms with different combinations of species. Higher environmental variability played a major role in driving population synchrony for the two species with lower salinity tolerances. We also found that population synchrony was higher in monocultures than in polycultures (when other species were present). On the other hand, population synchrony of Potamocypris species (high salinity tolerance) did not respond to different species combinations, under any amount of environmental variability. This finding emphasizes the importance of the relationship between environmental variability and species interactions, and suggests that in natural communities the presence of other species may change the expected effects of environmental variation on synchrony. By disrupting synchrony, biotic diversity potentially stabilizes metapopulations. Thus, the patterns of correlated environmental noise-induced synchrony derived from single species may not hold when populations are considered within the context of their multispecies communities.