Two plant species live along a gradient, from a rich temperate valley floor to halfway up a mountain slope.In the valley, the two plants are competitors, but going up the gradient their relationship changes and becomes more and more commensal.This change in their relationship is most likely the result of
A) greater predation.
B) greater food availability.
C) an increasingly stressful climate.
D) a decreasingly stressful climate.
E) less space, requiring closer growth habits.

Question

Quizplus · Accepted Answer

As the climate becomes more stressful with elevation (e.g., colder temperatures, less oxygen), the benefits one species may provide to another (such as shelter from the elements or shared resources without direct competition) can become more valuable, leading to a shift from competition to commensalism.

Two Plant Species Live Along a Gradient, from a Rich