Hybrid Inviability and Hybrid Sterility
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State
Hybrid inviability is a postzygotic barrier where a hybrid fails to survive to maturity; hybrid sterility is where a surviving hybrid cannot reproduce.
Show
A hybrid embryo that dies before birth shows inviability, while a mule, viable but sterile, shows sterility instead.
Watch for
Inviability blocks the hybrid from surviving at all — sterility lets it survive but blocks reproduction, a different failure point.