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SPECIAL FEATURE PLANT-MEDIATED INTERACTIONS BETWEEN ABOVE-AND BELOW-GROUND COMMUNITIES
 

Summary: SPECIAL FEATURE
PLANT-MEDIATED INTERACTIONS BETWEEN ABOVE- AND BELOW-GROUND COMMUNITIES
Direct and indirect root defences of milkweed
(Asclepias syriaca): trophic cascades, trade-offs and
novel methods for studying subterranean herbivory
Sergio Rasmann*, Alexis C. Erwin, Rayko Halitschke and Anurag A. Agrawal
Department of Ecology and Evolutionary Biology, Cornell University, Corson Hall, Ithaca, NY 14853-2701, USA
Summary
1. Entomopathogenic nematodes can function as indirect defence for plants that are attacked by
root herbivores. By releasing volatile organic compounds (VOCs), plants signal the presence of host
insects and thereby attract nematodes.
2. Nonetheless, how roots deploy indirect defences, how indirect defences relate to direct defences,
and the ecological consequences of root defence allocation for herbivores and plant biomass are
essentially unknown.
3. We investigate a natural below-ground tritrophic system, involving common milkweed, a spe-
cialist root-boring beetle and entomopathogenic nematodes, and asked whether there is a negative
genetic correlation between direct defences (root cardenolides) and indirect defences (emission of
volatiles in the roots and nematode attraction), and between constitutive and inducible defences.
4. Volatiles of roots were analysed using two distinct sampling methods. First, we collected
emissions from living Asclepias syriaca roots by dynamic headspace sampling. This method showed

  

Source: Agrawal, Anurag - Department of Ecology and Evolutionary Biology & Entomollogy, Cornell University

 

Collections: Environmental Sciences and Ecology