Question

The observation that island D. yakuba are more closely related to mainland D. yakuba than island D. yakuba are to D. santomea is best explained by proposing that D. santomea _____.

1) descended from a now-extinct, non-African fruit fly
2) arrived on the island before D. yakuba
3) descended from a single colony of D. yakuba, which had been introduced from elsewhere, with no subsequent colonization events
4) descended from an original colony of D. yakuba, of which there are no surviving members.

Answer 1

The observation that island and mainland D. yakuba are more closely related than island D. yakuba and D. santomea suggests that D. santomea descended from a non-African fruit fly.

Step-by-step explanation:

The observation that island D. yakuba are more closely related to mainland D. yakuba than island D. yakuba are to D. santomea is best explained by proposing that D. santomea descended from a now-extinct, non-African fruit fly. The close relatedness between island and mainland D. yakuba suggests a recent common ancestor, while the greater genetic distance between island D. yakuba and D. santomea suggests a longer period of divergence. Therefore, the most likely explanation is that D. santomea is descended from a non-African fruit fly that colonized the island.