In a lake, a certain native species of zooplankton is found evenly distributed in the water column. After introduction of a different species of zooplankton, the native species is only found in the shallow water zone. This is most likely an illustration of:

A) character displacement.
B) species richness.
C) primary succession.
D) secondary succession.
E) competitive exclusion.

Competitive Exclusion

A principle stating that two species competing for the same limiting resources cannot coexist at constant population values.

Character Displacement

The phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur, but are minimized or lost where the species' distributions do not overlap.

Primary Succession

An ecological succession that occurs on land that has not previously been inhabited by plants; no soil is present initially. See succession. Compare with secondary succession.