Final answer:
Criterion 2 for demonstrating character displacement involves showing significant differences in species traits in sympatric zones compared to allopatric zones.
Step-by-step explanation:
The question refers to the second criterion for demonstrating character displacement as defined by Schluter & McPhail in 1992.
While the original question does not explicitly state this second criterion, the concept of character displacement generally pertains to evolutionary changes in species traits where two species overlap geographically, typically leading to a divergence of traits such as size or shape to reduce competition.
Referring to the concept as it applies to biology and evolutionary studies, character displacement is often evidenced through morphological differences among species that share a common habitat.
For instance, Darwin's or Galapagos Finches exhibit a variety of bill shapes adapted to different food sources, which is a classic example of this theory.
Criterion 2 could involve demonstrating that the differences in traits between species are more pronounced in zones of sympatry (where species coexist) than in zones of allopatry (where species do not coexist).
To answer specifically about criterion 2 for character displacement, this would involve comparing the morphological traits of two species in different environments and showing a significant difference in those traits where the species coexist (sympatric zones) versus where they live separately (allopatric zones).