The Red Queen hypothesis predicts that outcrossing in pests can generate to new, rare, or lost genotypes that can be favorable when colonizing novel hosts. However, among haplodiploid spider mites (Tetranychus urticae)—where unfertilized females only have male offspring and fertilized females can determine the sex of each offspring—female offspring are more costly to make than males, while male offspring experience greater mortality. Here we assess the primary (sex ratio of offspring) and secondary sex ratios (sex ratio of adults) of spider mites across a diversity of host plant species (species) to test whether females produce more males on challenging host plants to improve outcrossing and to compensate for male loss.
Results/Conclusions
We found significantly unbalanced spider mite sex ratios across host species, and that these ratios corresponded to differences in host plant quality. These findings shed light on the role of sex in parasites and how sexual recombination can offer advantages in novel host environments.