Rocky Mountain juniper (Juniperus scopulorum)and one-seeded juniper (J. monosperma)have overlapping ranges. If pollen grains (which contain sperm cells)from one species are unable to germinate and make pollen tubes on female ovules (which contain egg cells)of the other species, then which of these terms is applicable?
A) behavioral isolation
B) mechanical isolation
C) hybrid breakdown
D) reduced hybrid viability

Question

Quizplus · Accepted Answer

This scenario describes mechanical isolation, where physical barriers prevent the sperm and egg from mating and fertilizing. The pollen grains from one species are unable to germinate and make pollen tubes on the female ovules of the other species, indicating that there are mechanical barriers preventing successful fertilization. Behavioral isolation refers to differences in behavior preventing mating, hybrid breakdown and reduced hybrid viability are related to problems observed in hybrids after fertilization occurs.

Rocky Mountain Juniper (Juniperus Scopulorum)and One-Seeded Juniper (J