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Why be female?


The evolution of dioecy (separate males and females) from hermaphroditism in higher plants has puzzled evolutionary biologists since Darwin1. An initial step towards the evolution of dioecy may often be the evolution and persistence of females within otherwise hermaphroditic populations1–6. This step is difficult because a nuclear gene for being female must provide a greater than twofold increase in female fitness for females and hermaphrodites to coexist stably5–8. It is unlikely that seed production would increase this much as a result of not producing pollen. Here I show that in buffalo gourd, seeds from females survive their first year in nature 2.8 times more frequently than seeds from hermaphrodites, apparently because seeds from hermaphrodites are mostly self-fertilized and selfing severely reduces seedling survival.

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Kohn, J. Why be female?. Nature 335, 431–433 (1988).

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