Two from one: Pitt research maps out evolution of genders from hermaphroditic...(and attraction through fighting or natur...)

For the current study, Ashman and Pitt postdoctoral research associate Rachel Spigler worked with a wild strawberry species in which the evolution of separate sexes is not complete, so hermaphrodites exist among male and female plants. Sex chromosomes in these plants have two locior positions of genes on a chromosomeone that controls sterility and fertility in males and the other in females. Offspring that inherit both fertility versions are hemaphrodites capable of self-breeding. Plants that possess one fertility and one sterility version become either male or female. Those with both sterility versions are completely sterile, cannot reproduce, and, thus, die out.

The single-sex plants breed not only with one another but also with hermaphroditic plants and pass on the mutation, which can result in single-sex offspring. (Sterile plants also can result, but plants with genes that favor the production of fertile offspring will be more successful.) When inbreeding depression in hermaphrodites is also considered, Ashman said, a gradual decline in the number of hermaphroditic plants is to be expected. Consequently, fewer chromosomes with both fertility versions of the loci will be passed on and the frequency of single-sex individuals will increase.

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