Variation inPseudonocardiaantibiotic defence helps govern parasite‐induced morbidity inAcromyrmexleaf‐cutting ants Journal Articles uri icon

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abstract

  • SummaryHost–parasite associations are potentially shaped by evolutionary reciprocal selection dynamics, in which parasites evolve to overcome host defences and hosts are selected to counteract these through the evolution of new defences. This is expected to result in variation in parasite‐defence interactions, and the evolution of resistant parasites causing increased virulence. Fungus‐growing ants maintain antibiotic‐producingPseudonocardia(Actinobacteria) that aid in protection against specialized parasites of the ants' fungal gardens, and current evidence indicates that both symbionts have been associated with the ants for millions of years. Here we examine the extent of variation in the defensive capabilities of the ant–actinobacterial association againstEscovopsis(parasite‐defence interactions), and evaluate how variation impacts colonies of fungus‐growing ants. We focus on five species ofAcromyrmexleaf‐cutting ants, crossing 12 strains ofPseudonocardiawith 12 strains ofEscovopsisin a Petri plate bioassay experiment, and subsequently conduct subcolony infection experiments using resistant and non‐resistant parasite strains. Diversity in parasite‐defence interactions, including pairings where the parasites are resistant, suggests that chemical variation in the antibiotics produced by different actinobacterial strains are responsible for the observed variation in parasite susceptibility. We evaluate the role this variation plays showing that infection of ant subcolonies with resistant parasite strains results in significantly higher parasite‐induced morbidity with respect to garden biomass loss. Our findings thus further establish the role ofPseudonocardia‐derived antibiotics in helping defend the ants' fungus garden from the parasiteEscovopsis, and provide evidence that small molecules can play important roles as antibiotics in a natural system.

authors

  • Poulsen, Michael
  • Cafaro, Matías J
  • Erhardt, Daniel P
  • Little, Ainslie EF
  • Gerardo, Nicole M
  • Tebbets, Brad
  • Klein, Bruce S
  • Currie, Cameron

publication date

  • August 2010