A hybrid zone forms where
- A
Two diverging populations remain fully isolated and never re-contact each other
- B
Two species are completely allopatric and cannot exchange alleles (no contact zone forms)
- Ccheck_circle
Two species' ranges overlap and produce hybrid offspring (often less fit)
- D
A single species spreads into new territory but encounters no related species there
Explanation
Hybrid zones are a natural laboratory: outcomes range from reinforcement (isolation strengthening) to fusion (merging) to stable hybrid populations.