Date of Award
12-2025
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Biological Sciences
Committee Chair/Advisor
Matthew Koski
Committee Member
Krissa Skogen
Committee Member
Jason Fridley
Abstract
Most flowering plant species are pollinated by animals, which transport their pollen from one individual to another. Because this relationship is essential for the successful reproduction of most flowering plants, the way a pollinator behaves as it forages can be important. Different pollinator species can have preferences for certain floral traits, making them more likely to visit a flower that is more appealing to them. If pollinators consistently choose to pollinate those plants with their preferred trait, flowers with the trait will reproduce more often, and over evolutionary time the desired traits may be more common in a plant population. This phenomenon is called pollinator-mediated floral evolution and can lead to pollination syndromes, which are a collection of floral traits that are suited to a plants’ most effective pollinator. For example, flowers pollinated by moths often bloom in the evening when moths are active and are strongly scented to better attract these pollinators in low light, making evening flowering and strong fragrance examples of moth pollination syndromes. While flower morphology, flower timing, and scent production are traits commonly associated with pollinator type, traits specific to pollen itself have not been previously investigated as traits that adhere to pollination syndromes. Evening primroses (Onagraceae) exhibit floral traits associated with different primary pollinators, making it an ideal system to test for differences in pollen traits among species with different pollinators. We tested whether Oenothera species primarily pollinated by hawkmoths and species primarily pollinated by bees differ in their pollen traits, specifically pollen longevity (the length of time a pollen grain remains viable) and pollen size. Hawkmoths travel much farther as they pollinate than bees do, leading to the prediction that hawkmoth-pollinated plants may evolve increased pollen longevity so that when pollen reaches another plant it is still viable (The Foraging Distance Hypothesis). On the other hand, the flowers of bee-pollinated species remain open for longer before wilting and bloom during the day, which may expose pollen to greater heat and drought, necessitating a higher pollen longevity in bee-pollinated plants to combat these stressful conditions (Floral Longevity Hypothesis). Using 4 hawkmoth- and 4 beepollinated Oenothera species, we conducted hand pollinations using pollen of different ages and measured pollen tube growth in the style tissue and number of seeds produced as proxies for pollen viability at each pollen age (0, 1, 3, 5, 10 days). Pollen longevity (estimated by both seed set and number of pollen tubes in the styles) did not differ between bee-pollinated species and hawkmoth-pollinated species, lending no support for the Foraging Distance Hypothesis or Flower Floral Hypothesis. However, pollen size did differ between species groups, with hawkmoth-pollinated species having larger pollen grains than bee-pollinated species. We conclude that pollen size but not pollen longevity may be introduced into the suite of recognized pollination syndromes.
Recommended Citation
Woldin, Maris, "Testing Whether Pollen Traits Adhere to Pollination Syndromes in Oenothera" (2025). All Theses. 4780.
https://open.clemson.edu/all_theses/4780