Description
Haldane’s rule applies to the vast majority of heterogametic organisms examined. These include both male heterogametic (XY or X0-type sex determination, such as found in mammals and Drosophila) and female heterogametic (ZW-type sex determination, such as found in birds and Lepidoptera) animals, and some dioecious plants such as Silene. It appears to be a general pattern associated with heterogamety.
Hybrid sterility and inviability increase reproductive isolation, which leads to speciation. The fact that evolution can produce such a similar pattern of isolation in a vast array of different organisms is striking. However, the actual mechanisms leading to this result in divergent taxa appear to vary. The basis by which the heterogametic sex becomes more susceptible to hybrid inferiority (sterility or inviability) has been a focus of theoretical and empirical explorations that have greatly enriched our understanding of sexual reproduction and speciation.
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