Two similar frog “species” have populations that are mostly allotropic to one another, but in a few places these species are sympatric and produce inviable hybrids where their distributions overlap. Both parent species prefer similar habitat, and their calls are very similar in allopatry. In laboratory preference tests, females of each species from allopatric populations will orient toward male calls from the other species almost as often as they orient toward calls from conspecifics. Is hybrid inviability most likely ecological or developmental? How do you know? What kind of reproductive isolation (use Dobzhansky’s terms, be specific) is currently occurring between the two parent species when they are in sympatry? What might you expect to eventually happen to the vocalizations of the parent species when they are in sympatry? What is the specific name for this process? What kind of reproductive isolation will start occurring between these two species when they are in sympatry after the process you named in question 3 has been occurring for many generations? If the parent species can produce viable, successful hybrids but prefer different parts of the habitat they share, what species concept could you use to say they are different species? What concept would classify them as the same species? (There are several options here, just list one concept that would correctly apply to each question.)