Degree

Doctor of Philosophy (PhD)

Department

The Department of Biological Sciences

Document Type

Dissertation

Abstract

Species interactions, specifically plant-insect interactions, are ubiquitous worldwide. Climate change will alter species interactions by affecting abiotic conditions, affecting species phenologies, interaction strengths, and physiological development. However, climate change impacts are often studied using individual species, with limited consideration quantifying the direct and indirect impacts of climate change species interactions. Using lab, field, and greenhouse experiments, I investigated how climate change will directly and indirectly affect species interactions while also fostering undergraduate research experiences using the monarch butterfly (Danaus plexippus)- milkweed (Asclepias sp.) system.

In North America, a widely planted, invasive milkweed species, Asclepias curassavica, negatively impacts monarch butterflies. I conducted a fully-factorial field experiment quantifying the indirect impacts of climate change on monarchs, as mediated through the invasive A. curassavica and native A. incarnata. Here, an ecological trap may be developing, driven by lethal increases in milkweed toxicity. Monarchs reared on the invasive A. curassavica at ambient conditions experienced improved performance, but under increased temperatures, monarchs fared much worse. Additionally, I conducted lab and field experiments to quantify the direct impacts of climate change on monarch butterflies and their protozoan parasite, Ophryocystis elektroscirrha (OE). OE threatens monarch populations by decreasing monarch performance, and empirical support is lacking on assessing the impacts of climate change on the interaction between parasites and hosts. Here, simultaneous parasite infection and increased temperatures act as a one-two punch for monarchs, decreasing development time, weights, melanism, and size.

I also designed a course-based undergraduate research experience (CURE) for early-division undergraduate students. Here, enrolled students conducted a fully-factorial, greenhouse competition experiment between invasive A. curassavica and two native milkweed species, A. incarnata and A. tuberosa. CURE student performance to that of upper-division students enrolled in a traditional ecology laboratory was also assessed. We found that A. curassavica is a commensal competitor, and that CURE participation can effectively educate and engage early division students in conducting scientific research. In summary, my dissertation highlights the importance of empirically testing the direct and indirect impacts of climate change on species and their interactions, while reinforcing that novel course structures can foster scientific inroads for early division undergraduate students.

Date

8-19-2019

Committee Chair

Elderd, Bret

Available for download on Saturday, August 15, 2020

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