In parapatric speciation, the two diverging species still have geographic contact but there is selection against genetic exchange due to a heterozygote disadvantage. Parapatric speciation differs from peripatric speciation because there is no contact between diverging populations in peripatric speciation.

In cases of sympatric speciation, two distinct species diverge from the same population within the same geographic location.

Allopatric literally means “other fatherland,” meaning that populations are geographically separate. Because populations are separate, they may use similar resources and be similar in structure. Allopatric populations come about due to geographic isolation, rather than behavioral isolation. Sympatric means “same fatherland,” meaning that populations are geographically overlapping and diverge due to behavioral isolation. As a result, they may also, show divergence from a common resource and original body structure. Where the two sympatric populations overlap, there is a hybrid zone. The two species may mate and produce hybrid offspring. 

Geographic speciation can be broadly divided into two categories: allopatric or sympatric. Sympatric speciations occurs when species diverge while living in the same geographic habitat. Allopatric speciation occurs when two populations of a species become separated (in this case by a highway), and over time become separate species.

Sympatric speciation, which most biologists agree is very uncommon, occurs when a population lives in the same habitat but diverges into two species. In this case, the bears occupied the same area but became isolated based on their diet. Note that for this to occur, selection on diet preference would need to be very strong.

Allopatric speciation is the correct answer. Allopatric speciation is when one species results in two species as a result of environmental barriers. In this instance, the separation of the planet is a physical barrier that leads to the Freg becoming two different species.

Plant polyploidy—the presence of more than one genotype—is not a geographic barrier. Plant polyploidy helps enable speciation.

Speciation is the event that occurs when two populations of a particular species can no longer interbreed. Speciation is not defined by physical barriers or by the time that two populations are separate from one another. In fact, two populations of the same species can be apart any distance or time, and if they can still interbreed they are considered the same species even if they look completely different.

Note that carrying capacity refers to the maximum number of individuals in a population that the natural resources of the surrounding environment can support. It is, essentially, the maximum healthy population size, and is not a measure of distance as implied in the answer choice.

Classifying species can be a difficult and particularly gray area. The key to this question, however, is that mules are sterile. This is an example of post-zygotic reproductive isolation. Hybrids that are sterile are not considered unique species.

Simply identifying traits or chromosome number is not enough to determine species. The defining factor of speciation is that the organism can no longer reproduce with the parent species, but can reproduce with other individuals of the species. Note that all breeds of dog still fall in the same species, despite the variety of different traits displayed across breeds, because they can produce offspring. Chromosome number also cannot solely determine species. Some genetic disorders result in aneuploidy in humans, in which individuals have too many or too few chromosomes.

Out of the choices, only temporal isolation can explain this phenomenon. Temporal isolation describes a type of reproductive isolation that comes about because the two species mate at different times.

Habitat isolation cannot explain this occurrence because we are told that the two species live in the same area. Hybrid breakdown also cannot be correct because the researcher was able to generate a viable hybrid (so he should reasonably be able to find first generation hybrids in the wild). Gametic isolation is also not correct because a hybrid was successfully generated.