In the Chiricahua Mountains in Arizona, a Species of Spider

Multiple Choice

In the Chiricahua Mountains in Arizona, a species of spider is found in both the woodland areas around streams and in the desert shrub areas. In the woodland areas, these spiders are under constant threat of predation from birds. Because of this, they spend little time in the exposed portion of their sheet webs. However, in the desert areas where birds are less of a threat, spiders constantly forage in the exposed portion of their webs. Offspring of matings between spiders from woodland and desert regions behave more like spiders from the desert habitat, even if they are living in the woodland area. The offspring quickly fall prey to birds, often before they have had a chance to reproduce. Over time, two different species arise. Was this a pre-mating or post-mating barrier?

A) pre-mating barrier, because individuals do not mate
B) post-mating barrier, because hybrids are produced but they do not reproduce
C) pre-mating barrier, because fertilization occurs but the hybrids are not viable
D) post-mating barrier, because hybrids are sterile and unable to mate