Haldane's rule is linked to extraordinary sex ratios and sperm length in stalk-eyed flies.

We use three allopatric populations of the stalk-eyed fly Teleopsis dalmanni from Southeast Asia to test two predictions made by the sex chromosome drive hypothesis for Haldane's rule. The first is that modifiers that suppress or enhance drive should evolve rapidly and independently in isolated populations. The second is that drive loci or modifiers should also cause sterility in hybrid males. We tested these predictions by assaying the fertility of 2,066 males derived from backcross experiments involving two pairs of populations and found that the proportion of mated males that fail to produce any offspring ranged from 38-60% among crosses with some males producing strongly female-biased or male-biased sex ratios. After genotyping each male at 25-28 genetic markers we found quantitative trait loci (QTL) that jointly influence male sterility, sperm length and biased progeny sex ratios in each pair of populations, but almost no shared QTL between population crosses. We also discovered th...