Additionally, although T. cristinae exists in only a small region (~30 km2) there are some areas where only one of the two host-plant species is present, and other areas where the two host-plant species can be found right next to one another. These different types of areas allow researchers to study two different types of speciation. In areas with only one of the host-plant species, they are able to study allopatry, which is when the different groups (populations) are separated by a physical barrier, so they can't reproduce with one another - in this case the areas with the other host-plant species are simply too far away. In areas where both host-plant species occur right next to each other, researchers can study parapatry - which is when groups (populations) of a species become two different species even though their habitats are only partially separated from one another. This means that members of the different groups are still able to reproduce with one another from time to time.
