Gause's experiments primarily on:
“Paramecium species” for gause's experiments primarily on. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Niche differentiation reduces overlap by separating species along resource, space, or time axes. Such partitioning can stabilize coexistence when each species performs relatively better under the conditions it uses most strongly. The remaining alternatives—“Birds”, “Diatoms”, “Warblers”—refer to different states, processes, or scales and therefore do not express the same causal relationship.
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 13