Document Type

Dissertation

Degree

Doctor of Philosophy

Major

Biology

Date of Defense

7-22-2020

Graduate Advisor

Aimee S. Dunlap

Committee

Zuleyma Tang-Martínez

Robert J. Marquis

Patricia G. Parker

Nathan Muchhala

Edward M. Spevak

Abstract

An aim of contemporary biology is elucidating the causes and consequences of phenotypic plasticity. Here, I approach this aim by exploring the eco-evolutionary dynamics of phenotypic plasticity and environmental variability in bumble bees (Apidae: Bombus), a congeneric clade of eusocial pollinating insects. Throughout their evolution, bumble bees have encountered spatiotemporal variability imposed by dynamic floral environments. Today, bumble bees additionally encounter spatiotemporal variability imposed by anthropogenic environmental change. In this dissertation, I explore how phenotypic plasticity affects how successfully bumble bees respond to environmental variability imposed by anthropogenic global change (Chapters 1 and 2) and their floral resources (Chapters 3 and 4). I focus on two notably plastic traits that have ecologically consequential implications: body size plasticity and behavioral plasticity. Using a combination of phenotypic, molecular, and modeling approaches - with data spanning field populations, biological collections, and laboratory colonies - the results of this work suggest that body size plasticity and behavioral plasticity are integral to the success of bumble bees in variable environments. I find that intraspecific trait variation is key to understanding population responses to environmental variability. Specifically, I find evidence that greater worker body size plasticity enables bumble bees to more successfully contend with anthropogenic environmental change (Chapters 1 and 2) and that behavioral variation is induced by floral variability (Chapters 3 and 4). Overall, this dissertation reveals that bumble bees respond to environmental variability in myriad ways and that these responses manifest at the individual-, colony-, and population-levels of biological organization. In addition to helping elucidate the eco-evolutionary dynamics of phenotypic plasticity and environmental variability, this work suggests that understanding the relationship between plasticity and bumble bee success in variable environments is integral to conserving these ecologically consequential pollinators.

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