Effects of competition, disturbance and productivity on the dynamics of inducible trophic polymorphism in tetrahymena vorax

Abstract

Inducible trophic polymorphism enables organisms to alter their trophic level when facing environmental changes, and therefore can ameliorate the intensity of competition. The freshwater ciliated protist Tetrahymena vorax was found to have three distinct phenotypic morphs with two trophic levels. Its carnivorous macrostomes consume intraspecific competitors and its bacterivorous pyriform microstome morph and tailed microstome morph indiscriminately. Cannibalism here indicates an extreme case of niche differentiation and resource utilization via phenotypic plasticity and significantly affects the dynamic equilibrium of T. vorax’s three morphs. By manipulating productivity level, disturbance frequency and the presence or absence of an interspecific competitor species Colpdium striatum, I demonstrated the dynamic transformations of T. vorax’s three morphs and endeavored to explain the underlying mechanisms. In this study, I also tested some classic assumptions about phenotypic tradeoffs in T. vorax and hence clarified some misunderstandings and proposed novel hypotheses.