Cooperative interactions among females can lead to even more extraordinary sex ratios

Abstract Hamilton's local mate competition theory provided an explanation for extraordinary female-biased sex ratios in a range of organisms. When mating takes place locally, structured populations, ratio is favored to reduce between related males, and provide more mates males. However, there are number wasp species which the appear female biased than predicted by theory. It has been hypothesized that additional bias these results from cooperative interactions females. We investigated theoretically extent cooperation females can interact with favor even ratios. found (i) lead alone, (ii) be when occurs offspring mothers before dispersal, rather siblings after dispersal. Our models formally confirm verbal predictions made previous experimental studies, could applied Specifically, help explain biases Sclerodermus Melittobia wasps, although quantitative comparisons data suggest some factors may operating.