DIVERGENCE OF MEIOTIC DRIVE‐SUPPRESSION SYSTEMS AS AN EXPLANATION FOR SEX‐BIASED HYBRID STERILITY AND INVIABILITY

hybrids (Haldane's rule), and the tendency of the X chromosome to harbor the genetic elements that cause this sex bias in hybrid fitness. I suggest that divergence of meiotic drive systems on the sex chromosomes can explain these observations. The theory follows from two simple facts. First, sex chromosomes are particularly susceptible to the forces of meiotic drive. Second, divergence of meiotic drive systems can cause hybrid sterility and in viability. The main objection to the theory is that meiotic drive is apparently rare, whereas the observed pattern of hybrid fitness is widespread. I answer this objection by showing that divergence of meiotic drive systems can explain the two generalizations even if large departures from Mendelian segregation are rarely observed.