Biol 6 - Plant Sex

Flower: a specialized shoot with 4 whorls of modified leaves sepals (calyx) sterile petals (corolla) stamen (filament + anther) pistil (stigma + style + ovary) H F Dimorphic gender expression M the presence of two sexual mating types in populations M ca. 10% of all angiosperm species Cosexual gender expression H H F F H M combine both gender functions within individuals Monomorphic the presence of a single sexual mating type in a population F M H H F F Male-sterility mutation F M Female-sterility mutation M Challenges & complications… •! Lack sophisticated sensory abilities, behaviors •! Rooted to the ground •! Dependent on vectors for pollen dispersal •! Modular construction & the “packaging” of gender •! Cosexual gender expression & the potential for self-fertilization Finding potential mates Biotic pollination •! Exploit sensory systems of animals Visual cues (color, nectar guides) Morphology (symmetry, tubes) Olfactory Mimicry (sexual, resource) Rewards (pollen, nectar) •! Floral specialization •! Pollination “syndromes” Finding potential mates Abiotic pollination •! Use wind/water to move pollen •! Not very efficient •! Floral specialization Arum volatiles Arum volatiles Identified active odor compounds in Arum inflorescences… carrion volatiles Characterized the response of flies to odor of Arum flowers… Stensmyr et al. Nature (2002) Stensmyr et al. Nature (2002) Same active odor compounds in Arum inflorescences and carrion Finding potential mates Arum volatiles Pollination syndromes carrion volatiles Same active odor compounds in Arum inflorescences and carrion Blowfly antennae responded identically to sulphide odors from carrion and Arum •! Facilitate finding mates” OR Self pollination/fertilization world famous selfer, Arabidopsis thaliana The evolution of selfing is perhaps the most common transition in angiosperm evolution Stensmyr et al. Nature (2002) Self-fertilization among flowers on the same plant Self-fertilization seems like a good idea reasonable under some circumstances •! Isolated individuals •! Plants at the edge of a species range •! In years with poor pollinator service •! Locally adapted populations within a flower Anthoxanthum odoratum (Poaceae) Ability to self-fertilize Self-fertilization seems like a good idea , but… inbreeding depression often a problem Some groups tolerate self-fertilization… and seemingly have adaptations to promote it! reasonable under some circumstances •! Isolated individuals •! Plants at the edge of a species range •! In years with poor pollinator service •! Locally adapted populations or evolved as a consequence of it (selfing) Outcrossed plants Selfed plants Flowers do not open; obligate selfers (e.g., violets) IBD in white clover (Trifolium repens) Some lineages of plants tolerate self-fertilization Eichhornia crassipes (Pontederiaceae) outcrossing Some lineages of plants tolerate self-fertilization selfing (A) Brazil - outbreeding population Amsinckia spp. (Boraginaceae) 5 generations of self-fertilization Significant IBD Flowers from selfing populations are smaller than those in outcrossing pop’lns Plants from selfing populations make fewer flowers than those in outcrossing pop’lns Outcross >200 vs. Selfed <100 outcrosser selfer Prediction for inbreeding depression? (B) Jamaica - selfing (inbred) population) 5 generations of self-fertilization No significant IBD