The x-axis and y-axis in phase-plane diagram usually represent:
“Density of species 1 and species 2” for the x-axis and y-axis in phase-plane diagram usually represent. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Species interactions are classified by their net effects on the fitness of each participant, but those effects can change with density, resource supply, life stage, and environmental stress. Competition reduces access to shared limiting factors, whereas predation and parasitism transfer resources from victim to consumer. The remaining alternatives
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 13-14
