Sex-biased oviposition by a nursery pollinator on a gynodioecious host plant: Implications for breeding system evolution and evolution of mutualism.

Dioecy, a breeding system where individual plants are exclusively male or female, has evolved repeatedly. Extensive theory describes when dioecy should arise from hermaphroditism, frequently through gynodioecy, where females and hermaphrodites coexist, and when gynodioecy should be stable. Both pollinators and herbivores often prefer the pollen-bearing sex, with sex-specific fitness effects that can affect breeding system evolution.

Dramatic vestigialization of floral fragrance across a transition from outcrossing to selfing in Abronia umbellata (Nyctaginaceae).

Premise Of The Study: Vestigialization of traits that no longer enhance fitness is a common theme in evolution. Plants often use colorful, scented flowers to attract pollinators that mediate outcross pollination. After an evolutionary shift from outcrossing to self-fertilization, where cross-pollination is no longer necessary, attractive traits may be reduced, especially because these traits may also attract herbivores.