2020 ESA Annual Meeting (August 3 - 6)

COS 15 Abstract - Diet indirectly alters parasite resistance through the gut microbiome in monarch butterflies

Erica Harris1, Tiffanie Y. Alcaide1, Kandis L. Adams1, Mahal J. Bugay2,3, Keisha Baffour-Addo1, Ava H. Salmi1, Anna J. Zelaya1, Mark D. Hunter4, Nicole M. Gerardo1 and Jacobus C. de Roode1, (1)Department of Biology, Emory University, Atlanta, GA, (2)Evolution, Ecology, and Population Biology program, Washington University in St. Louis, St. Louis, MO, (3)Biology, Agnes Scott College, Decatur, GA, (4)Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI
Background/Question/Methods

Host defense mechanisms against parasites undergo strong selection, and it is increasingly clear that microbial symbionts can provide such defenses. Monarch butterflies (Danaus plexippus) have undergone a long coevolution with their toxic milkweed host plants and detrimental protozoan parasites. Previous work has shown that monarchs obtain resistance to their parasites when feeding on milkweeds with higher concentrations of secondary chemicals called cardenolides. Like all other animals, monarchs host a diversity of microbes in their guts, and we have tested the hypothesis that plant-conferred resistance is the result of an alteration of the monarch gut microbial community to an anti-parasitic state. We fed larvae on different milkweed plant species -known to vary in their cardenolide concentration - and dissected the larval midgut, sequenced bacterial 16s rDNA sequences, and quantified bacterial abundance with qPCR.

Results/Conclusions

Results demonstrate that larvae fed on these different plants had different gut microbial communities. In follow-up experiments, we transferred fecal pellets from caterpillars reared on high-cardenolide plants to caterpillars reared on low-cardenolide plants. This resulted in increased parasite resistance as well as increased gut microbial community diversity and abundance, suggesting that the gut microbiota are modulated by high-cardenolide milkweed and confer protection against parasite infection. Overall, these results suggest that gut microbes alter the resistance phenotypes of monarchs and that milkweeds play an important role in the coevolution between monarchs, parasites and gut microbes.