In order to determine if individuals from separate populations are indeed distinct species, drosophila biologists often test to see if individuals from different populations will mate with each other. this is an application of the species concept.

Biological species contest.

Explanation:

Different species concept are introduced to describe the exact definition and classification of species. Some species concept are biological species contest, morphological species concept and ecological species contest.

According to biological species contest, the group of individual that can breed among themselves and not with the other group. Here, the Drosophila species has been classified by the biologist depending on their mating ability to their group of individual only.

Thus, the answer is biological species contest.