Document Type

Thesis

Degree

Master of Science

Major

Biology, Evolution

Date of Defense

7-13-2021

Graduate Advisor

Dr. Nathan Muchhala

Committee

Dr. Nathan Muchhala

Dr. Aimee Dunlap

Dr. Kyra Krakos

Abstract

Despite a storied history of pollination research, little information exists on how the unique characteristics of individual pollinators effect patterns of pollen dispersal. As these patterns of pollen dispersal inform our understanding of floral evolution, filling in this knowledge gap is imperative. I attempted to do so by analyzing two different outcomes of pollen dispersal: 1) pollen carryover, and 2) geitonogamy (i.e., intra-plant movements). For the pollen carryover, I analyzed the results of an experimental study in which bats in flight cages removed pollen from the male flower of a Burmeistera glabrata plant, and then visited 10 female flowers of B.glabrata. The goal was to determine the proportions of pollen grains deposited by the bats on each female flower and how grooming in-between visits affected these proportions. In general, bat carryover-curves were similar to those of published work with bees, with the greatest proportion of pollen deposited on the first couple female flowers followed by a steep decline in the proportion reaching subsequent flowers. Grooming had a significant effect on the proportion of grains deposited. However, when the sexes were analyzed separately, significance only remained for female bats. Furthermore, I found females groom more than males. This suggests that increased grooming allows females to consume more pollen, an important way to increase nutrient uptake before and during pregnancy. Patterns of pollen dispersal may fluctuate annually based on the reproductive stage of female bats.

I also analyzed results from a Missouri insect visitation study of Asclepias species to measure the potential for geitonogamous movements. Overall, Bombus sp. and Apis mellifera, were the most abundant visitors, with Halictidae sp., dominating at A.tuberosa. Visitors were more likely to move within the plant than to leave, increasing the possibility for geitonogamous pollen transfer. I discussed results within the context of how the unique traits and behaviors of each Bombus, Apis, and Halictidae may affect the rates of geitonogamy.

Findings from both studies highlight the need for caution in generalizing patterns of pollen dispersal between pollination systems. Continued studies into pollinator behaviors will better inform our understanding of floral evolution.

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