Two related plant species can be cross-pollinated in the lab, producing viable seeds, but the resulting hybrid plants are sterile. In nature they grow side by side and are visited by the same pollinators. The most relevant isolation mechanism here is
- A
Prezygotic — behavioral isolation (different pollinator preferences)
- Bcheck_circle
Postzygotic — hybrid sterility (reduced hybrid fertility)
- C
Prezygotic — temporal isolation (different flowering times)
- D
Prezygotic — gametic isolation (incompatible pollen and stigma)
Explanation
Hybrids form (so prezygotic barriers fail) but the hybrids are sterile — that is hybrid sterility, a postzygotic mechanism.