Contemporary Evolution during Global Range Expansion in the Monarch Butterfly
General Material Designation
[Thesis]
First Statement of Responsibility
Freedman, Micah
Subsequent Statement of Responsibility
Strauss, Sharon Y;Ramirez, Santiago R
.PUBLICATION, DISTRIBUTION, ETC
Name of Publisher, Distributor, etc.
University of California, Davis
Date of Publication, Distribution, etc.
2020
PHYSICAL DESCRIPTION
Specific Material Designation and Extent of Item
244
DISSERTATION (THESIS) NOTE
Dissertation or thesis details and type of degree
Ph.D.
Body granting the degree
University of California, Davis
Text preceding or following the note
2020
SUMMARY OR ABSTRACT
Text of Note
Species that expand their geographical ranges provide unique opportunities to test fundamental questions in ecology and evolution. Monarch butterflies (Danaus plexippus) are best-known from their ancestral North American range but have greatly expanded their range over recent evolutionary history. The monarch's global range expansion involves three independent expansion events, each characterized by an independent loss of migratory behavior and convergent genomic evolution associated with this loss of migration. Monarchs encounter novel selective environments in their introduced range, including novel host plant species and assemblages. This dissertation focuses on the monarch's global range expansion as an evolutionary experiment. In Chapter 1, I use reduced-representation sequencing of 281 monarchs from North America and 15 locations throughout the Pacific to reconstruct the monarch's Pacific range expansion. In Chapter 2, I focus on the reasons for the monarch's loss of migration and test whether this process is best explained by the absence of migration-associated environmental cues or a breakdown of the mechanisms associated with sensing and integrating these cues. In Chapter 3, I use a combination of more than 6,000 museum specimens and 1,000 experimentally reared monarchs to test how loss of migration has impacted monarch wing morphology, and show that range expansion and loss of migration have both influenced wing morphology in monarchs. In Chapter 4, I focus on host plant adaptation across the monarch's global range and find evidence for local adaptation in larval performance metrics, despite strong inherent differences in milkweed host species and monarch populations. This dissertation combines approaches from population genetics, insect physiology, functional morphology, and chemical ecology and adds to our understanding of (1) contemporary evolution during species range expansions and (2) the basic biology of the monarch, an iconic but increasingly imperiled butterfly species.