Rising algae density affects the influences of Daphnia magna on the competitive outcome between Brachionus rotifer species.

Superior competitors are known to regulate community structure by influencing competitive outcomes between species of inferior competitors with overlapping ecological niches. However, more research is needed to obtain a detailed understanding of the ecological process.We examined how the superior competitor Daphnia magna influenced competition–exclusion between two coexisting Brachionus rotifer species.Brachionus angularis was no longer the superior competitor when D. magna was introduced into the cultured Brachionus calyciflorus + B. angularis system. Small‐sized D. magna (1.6–1.9 mm in body length) mediated population dynamics and facilitated the persistence of the two Brachionus species, while large‐sized D. magna (2.0–2.3 mm in body length) excluded only B. angularis at the high food level (3 × 106 cells/ml Chlorella) or both rotifer species at the low food level (1 × 106 cells/ml Chlorella).These findings indicate that the different body sizes of a superior competitor species can reverse competitive results between inferior competitor species in relation to food abundance.Our results highlight the dynamic nature of populations in multispecies communities and the need to understand species interactions in relation to their environment. [ABSTRACT FROM AUTHOR]