Are eastern and western monarch butterflies distinct populations? A review of evidence for ecological, phenotypic, and genetic differentiation and implications for conservation. Issue 7 (2nd May 2021)

• Record Type: Journal Article
• Authors: Freedman, Micah G.; de Roode, Jacobus C.; Forister, Matthew L.; Kronforst, Marcus R.; Pierce, Amanda A.; Schultz, Cheryl B.; Taylor, Orley R.; Crone, Elizabeth E.
• Is Part Of: Conservation science and practice. Volume 3:Issue 7(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-05-02
• Subjects: conservation -- migration -- monarch butterfly -- population ecology -- population genetics; Biodiversity conservation -- Periodicals; Biodiversity conservation; Periodicals; 333.951605
• DOI: 10.1111/csp2.432
• Languages: English
• ISSNs: 2578-4854

Abstract

Abstract: Monarch butterflies are a species of conservation priority due to declining overwintering populations in both eastern and western North America. Declines in western overwintering monarchs—more than 99.9% since monitoring began—are especially acute. However, the degree to which western monarchs are a distinct biological entity is uncertain. In this review, we focus on phenotypic and genetic differentiation between eastern and western monarchs, with the goal of informing researchers and policy‐makers who are interested in monarch conservation. Eastern and western monarchs occupy distinct environments and show some evidence for phenotypic differentiation, particularly for migration‐associated traits, though population genetic and genomic studies suggest that they are indistinguishable from one another. We suggest future studies that could improve our understanding of differences between eastern and western monarchs. We also discuss the concept of adaptive capacity in eastern and western monarchs as well as non‐migratory populations outside of the monarch's primary North American range. Finally, we discuss the prospect of completely losing migratory monarchs from western North America and what this entails for monarch conservation. Abstract : Monarch butterflies are a species of conservation significance, and migratory western North American monarch butterflies are at especially high risk of local extirpation. This review article contextualizes the decline of western monarchs by reviewing research on their status as a distinct population from eastern monarchs, with an emphasis on studies of genetic, phenotypic, and ecological differentiation.