Graduate Defense: Emily Sun

Thesis Information

Title: Assessing The Effects Of Non-Native Flowering Plants And Anti-Herbivory Plastic (Vexar®) Tubes On Insect Visitation To Native Plants

Program: Master of Science in Biology

Advisor: Dr. Ian Robertson, Biological Sciences

Committee Members: Dr. David Pilliod, Biological Sciences (Co-Chair); and Dr. James Smith, Biological Sciences

Abstract

Bees (Hymenoptera: Apoidea) are among the most prominent pollinators of the flowering plants and play an essential role in maintaining ecosystem function. Disruption of plant-pollinator interactions is a growing global concern because of the implications for biodiversity, ecosystem health, and agriculture. The incursion of non-native plants globally is seen to adversely affect not only native plants, but the resident pollinators as well, as the non-natives alter plant-pollinator communities. For my first chapter, I examined the effects of a non-native weed, Sisymbrium altissimum (tall tumblemustard), on bee visitation to nearby native Sphaeralcea munroana (Munro’s globemallow) and whether these effects were dependent on what specific bee genus was visiting. Overall, I found little evidence that the ratio of tumblemustard:globemallow blooms influenced pollinator visits to globemallow. Across treatments, many bees focused their visits on the native species. However, differences in response may exist among bee genera. Focusing on the more common bees at my study site, there was some indication that generalist bees, Andrena and Lasioglossum, responded positively to tumblemustard blooms, while globemallow specialists, Colletes and Diadasia, responded positively to globemallow blooms. For my second chapter, I investigated whether Vexar®, an anti-herbivory plastic tube used in restoration planting, prevents bees from visiting flowers. Given the combined effects of accelerated fire regimes and ecosystem degradation in the sagebrush steppe (and the subsequent costly restorations), it is prudent to understand whether these tubes have deterrent effects on bees, through physical exclusion, visual deterrence, or both. To test these possibilities, I altered the presence and color of Vexar protecting two native plant species, Munro’s globemallow and shaggy fleabane, and observed the visitation rates of bees to flowers in a controlled field setting. I also examined the spectral signatures produced by Vexar painted in different colors and related this information to the color spectrum detected by bees. The results indicate that Vexar does not prevent bees from visiting the flowers inside, and there was no evidence that Vexar (or its color) influenced visitation rates to flowers in ways that would warrant reconsideration or alteration of its use in restoration. Future work regarding both of these experiments should include measurements of native plant seed set to elucidate whether tumblemustard or Vexar interfere with native plant pollination success.