During the observations of a species of blue moon butterflies on the Samoan islands of Upolu and Savaii,99% of the butterflies were originally female and only 1% were male,but in only five years the male:female sex ratio had returned to nearly the expected 1:1.What caused this?

Question

Quizplus · Accepted Answer

This change in the sex ratio is most likely due to evolutionary changes in the butterflies which allowed them to suppress the male-killing effect of Wolbachia. This is supported by research on other insect species which have also evolved to overcome Wolbachia-induced sex ratio bias. Option A is incorrect because it implies that Wolbachia was actively killing male butterflies initially but lost this ability, whereas the more likely scenario is that female-biased sex ratio was due to male-killing by Wolbachia. Option C is incorrect because both options are not equally likely.

During the Observations of a Species of Blue Moon Butterflies