The monarch butterfly, Danaus plexippus, is famous for its spectacular annual migration across North America, recent worldwide dispersal, and orange warning coloration. Despite decades of study and broad public interest, we know little about the genetic basis of these hallmark traits. Recently, by sequencing and analyzing 101 Danaus genomes from around the globe, we uncovered the history of the monarch’s evolutionary origin and global dispersal, characterized the genes and pathways associated with migratory behavior, and identified the discrete genetic basis of warning coloration. The results substantially changed our understanding of this classic system, showing, for instance, that D. plexippus was ancestrally migratory and dispersed out of North America to occupy its broad distribution. We found striking signatures of selection associated with suites of genes involved in neurogenesis, development, and metabolism but the strongest signatures of selection centered on flight muscle function, resulting in greater flight efficiency among migratory monarchs, and that variation in monarch warning coloration was controlled by a gene not previously implicated in insect pigmentation. We are now working to determine the precise environmental cues that trigger migratory behavior and genetically dissect the migratory syndrome – including behavior, physiology and morphology. This research is of particular importance now because monarch migration is currently experiencing a notable decline. Our work is documenting the evolutionary, genetic, and behavioral distinctiveness of North American monarchs and identifying the functional molecular basis of this amazing natural phenomenon.

Selected Publications

Dockx, C., K. A. Hobson, M. Kronforst, K. J. Kardynal, C. Pozo, J. Schuster, D. A. Green II, M. Dix, S. Nallu and S. Lynch. 2023. Migration of Eastern North American monarch butterflies via the South-east and the Atlantic: evidence from stable isotopes, thin layer chromatography, DNA and phenotype. Biological Journal of the Linnean Society 139: 294–325.

Tenger-Trolander, A., C. R. Julick, W.  Lu, D. A. Green, K. L. Montooth and M. R. Kronforst. 2023. Seasonal plasticity in morphology and metabolism differs between migratory North American and resident Costa Rican monarch butterflies. Ecology and Evolution 13: e9796. bioRxiv preprint

Tenger-Trolander, A. and M. R. Kronforst. 2020. Migration behaviour of commercial monarchs reared outdoors and wild-derived monarchs reared indoors. Proc. R. Soc. B 287: 20201326.  UChicago Medicine News  Phys.org

Talla, V., A. A. Pierce, K. L. Adams, T. J. B. de Man, S. Nallu, F. X. Villablanca, M. R. Kronforst and J. C. de Roode. 2020. Genomic evidence for gene flow between monarchs with divergent migratory phenotypes and flight performance. Molecular Ecology 29: 2567– 2582. ScienceDaily  YouTube

Tenger-Trolander, A., W. Lu, M. Noyes and M. R. Kronforst. 2019. Contemporary loss of migration in monarch butterflies. Proc. Natl. Acad. Sci. USA 116: 14671-14676.  Nature News & Views  Science Magazine  The Atlantic  ScienceDaily  Sciworthy  Anthropocene

Green, D. A. and M. R. Kronforst. 2019. Monarch butterflies use an environmentally sensitive, internal timer to control overwintering dynamics. Molecular Ecology 28: 3642-3655. Dryad Data  ScienceDaily  EarthSky

Zhan, S., W. Zhang, K. Niitepold, J. Hsu, J. F. Haeger, M. P. Zalucki, S. Altizer, J. C. de Roode, S. M. Reppert and M. R. Kronforst. 2014. The genetics of monarch butterfly migration and warning colouration.  Nature 514: 317-321.  Nature News & Views  Science Magazine  NY Times  National Geographic  Washington Post  NBC News

Pierce, A. A., M. P. Zalucki, M. Bangura, M. Udawatta, M. R. Kronforst, S. Altizer, J. F. Haeger and J. C. de Roode. 2014. Serial founder effects and genetic differentiation during worldwide range expansion of monarch butterflies.  Proc. R. Soc. B 281: 20142230.