Abstract Detail



Symbioses: Plant, Animal, and Microbe Interactions

Lynn, Austin [1], Piotter, Emelyn [1], Galen, Candace [1].

A Sticky Situation: selective pressure on pollen grain sculpture through differential pollen adherence.

Sexual selection acts through forces that favor increased mating probability for one of the sexes. Since many flowering plants depend on animal pollinators to distribute pollen grains to receptive stigmas, there may be selective pressure for optimal adherence to pollinators and for successful transfer to the stigma. Echinate (spiny) pollen grains are often associated with insect pollination, wherein spines are thought to protect the male gametophyte from consumption by pollinators. To test the hypothesis that pollen spine traits differ between plant species with contrasting levels of dependence on pollinators, we compared pollen spine characteristics between obligate sexual and apomictic Taraxacum (dandelion) species. Next, we conducted field experiments to test the hypothesis that spine traits determine whether or not pollen is picked up by a bee (Bombus spp.) or transferred to a stigma. We found that pollen spines of sexual dandelions were longer and further apart than those of asexual species. In the field experiments, greater spine separation was the strongest predictor of pollen adherence to flower-visiting bees, while greater spine length best predicted pollen transfer and germination on recipient stigmas. Since spine distance and spine length are positively correlated, these results show two complimentary targets of selection on pollen grain sculpture, and suggest that selection in sequential stages of the pollination process may have favored the repeated evolution of echinate pollen grains in entomophilous lineages. Furthermore, we suggest a loss of selective pressure on pollen sculpture under the loss of sex in apomictic Taraxacum. Future studies should investigate additive genetic variance and heritability underlying spine characteristics, as well as if spine traits confer greater male fertility in terms of seed siring success.


1 - University of Missouri, Division of Biological Sciences, 202 Tucker Hall, Columbia, MO, 65211, USA

Keywords:
pollination
Sexual Selection
exine
Asteraceae
stigma.

Presentation Type: Oral Paper
Session: 35, Symbioses: Plant, Animal, and Microbe Interactions
Location: 104/Mayo Civic Center
Date: Wednesday, July 25th, 2018
Time: 10:15 AM
Number: 35009
Abstract ID:386
Candidate for Awards:None


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