Journal of Chemical Ecology

, Volume 41, Issue 6, pp 520–523 | Cite as

Secondary Defense Chemicals in Milkweed Reduce Parasite Infection in Monarch Butterflies, Danaus plexippus

  • Camden D. Gowler
  • Kristoffer E. Leon
  • Mark D. Hunter
  • Jacobus C. de Roode
Rapid Communication

Abstract

In tri-trophic systems, herbivores may benefit from their host plants in fighting parasitic infections. Plants can provide parasite resistance in two contrasting ways: either directly, by interfering with the parasite, or indirectly, by increasing herbivore immunity or health. In monarch butterflies, the larval diet of milkweed strongly influences the fitness of a common protozoan parasite. Toxic secondary plant chemicals known as cardenolides correlate strongly with parasite resistance of the host, with greater cardenolide concentrations in the larval diet leading to lower parasite growth. However, milkweed cardenolides may covary with other indices of plant quality including nutrients, and a direct experimental link between cardenolides and parasite performance has not been established. To determine if the anti-parasitic activity of milkweeds is indeed due to secondary chemicals, as opposed to nutrition, we supplemented the diet of infected and uninfected monarch larvae with milkweed latex, which contains cardenolides but no nutrients. Across three experiments, increased dietary cardenolide concentrations reduced parasite growth in infected monarchs, which consequently had longer lifespans. However, uninfected monarchs showed no differences in lifespan across treatments, confirming that cardenolide-containing latex does not increase general health. Our results suggest that cardenolides are a driving force behind plant-derived resistance in this system.

Keywords

Resistance Insect immunity Herbivory Asclepias Danaus plexippus Ophryocystis elektroscirrha 

References

  1. Agrawal AA, Konno K (2009) Latex: a model for understanding mechanisms, ecology, and evolution of plant defense against herbivory. Annu Rev Ecol Evol Syst 40:311–331CrossRefGoogle Scholar
  2. Agrawal AA, Petschenka G, Bingham RA, Weber MG, Rasmann S (2012) Toxic cardenolides: chemical ecology and coevolution of specialized plant-herbivore interactions. New Phytol 194:28–45PubMedCrossRefGoogle Scholar
  3. R Core Development Team (2013) R: a language and environment for statistical computing., Retrieved from http://www.R-project.org
  4. Cory JS, Hoover K (2006) Plant-mediated effects in insect-pathogen interactions. Trends Ecol Evol 21:278–286PubMedCrossRefGoogle Scholar
  5. de Roode JC, Pedersen AB, Hunter MD, Altizer S (2008) Host plant species affects virulence in monarch butterfly parasites. J Anim Ecol 77:120–126PubMedCrossRefGoogle Scholar
  6. de Roode JC, de Castillejo CL, Faits T, Alizon S (2011a) Virulence evolution in response to anti-infection resistance: toxic food plants can select for virulent parasites of monarch butterflies. J Evol Biol 24:712–722PubMedCrossRefGoogle Scholar
  7. de Roode JC, Rarick RM, Mongue AJ, Gerardo NM, Hunter MD (2011b) Aphids indirectly increase virulence and transmission potential of a monarch butterfly parasite by reducing defensive chemistry of a shared food plant. Ecol Lett 14:453–461PubMedCrossRefGoogle Scholar
  8. Keating ST, Yendol WG, Schultz JC (1988) Relationship between susceptibility of gypsy-moth larvae (Lepidoptera, Lymantriidae) to a baculovirus and host plant foliage constituents. Environ Entomol 17:952–958CrossRefGoogle Scholar
  9. Lindsey E, Altizer S (2009) Sex differences in immune defenses and response to parasitism in monarch butterflies. Evol Ecol 23:607–620CrossRefGoogle Scholar
  10. McLaughlin RE, Myers J (1970) Ophryocystis elektroscirrha sp. n., a Neogregarine pathogen of the monarch butterfly Danaus plexippus (L.) and the Florida queen butterfly D. gilippus berenice Cramer. J Protozool 17:300–305CrossRefGoogle Scholar
  11. Sternberg ED, Lefèvre T, Li J, de Castillejo CL, Li H, Hunter MD, de Roode JC (2012) Food plant derived disease tolerance and resistance in a natural butterfly-plant-parasite interaction. Evolution 66:3367–3376PubMedCrossRefGoogle Scholar
  12. Zehnder CB, Hunter MD (2007) Interspecific variation within the genus Asclepias in response to herbivory by a phloem-feeding insect herbivore. J Chem Ecol 33:2044–2053PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2015

Authors and Affiliations

  • Camden D. Gowler
    • 1
    • 2
  • Kristoffer E. Leon
    • 1
  • Mark D. Hunter
    • 2
  • Jacobus C. de Roode
    • 1
  1. 1.Biology DepartmentEmory UniversityAtlantaUSA
  2. 2.Department of Ecology and Evolutionary BiologyUniversity of Michigan, Kraus Natural Sciences BuildingAnn ArborUSA

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