Which of the following are examples of postzygotic reproductive barriers? (Select all that apply) Two different beetle species inhabit different tree species in the same forest Two different hummingbird species in an area breed during different seasons Two different seal species interbreed frequently, but their offsring are sterile Two different oak tree species interbreed frequently, and produce hybrid offspring that grow poorly and have particularly high mortality Two different fungus species interbreed occasionally, but their hybrid offspring are incapable of reproducing.