If a population of gallflies occurred in an area where birds were present but parasitoid wasps were absent, which type of selection is most likely to affect gall size?

Question

Quizplus · Accepted Answer

In the absence of parasitoid wasps, birds would likely prey on the gallflies, preferring either the smallest or largest galls depending on which are easier to find or consume. This would lead to directional selection, where one extreme of gall size becomes more advantageous, either larger or smaller galls, depending on the birds' predation patterns.

If a Population of Gallflies Occurred in an Area Where