Scientists have found that flies in the northern parts of the United States are more inclined to have multiple partners in order to reduce the occurrence of an X chromosome which causes the production of only female offspring.
This selfish genetic element (SGE) tries to replicate itself by killing sperm that carry the Y chromosome, but has the side-effect that males with the gene produce fewer sperm. Female fruit flies take advantage of this weakness by having several mates, increasing the chances that SGE-free males, with a higher sperm count, will father their offspring.
The team, in collaboration with the Universities of Exeter, Leeds and Madrid, proved a correlation between the number of mates and the prevalence of the gene by collecting samples of fruit flies from seven sites in the United States.
It was already known that southern populations of the fly had a higher prevalence of the gene compared to those
... read more at: https://www.sciencedaily.com/releases/2014/04/140401210423.htm