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Ecology, 90(9), 2009, pp. 23932404 2009 by the Ecological Society of America
 

Summary: Ecology, 90(9), 2009, pp. 23932404
2009 by the Ecological Society of America
Cardenolides, induced responses, and interactions between
above- and belowground herbivores of milkweed (Asclepias spp.)
SERGIO RASMANN,1
ANURAG A. AGRAWAL, SUSAN C. COOK, AND ALEXIS C. ERWIN
Department of Ecology and Evolutionary Biology, Corson Hall, Cornell University, Ithaca, New York 14853-2701 USA
Abstract. Theory has long predicted allocation patterns for plant defense against
herbivory, but only recently have both above- and belowground plant defenses been
considered simultaneously. Milkweeds in the genus Asclepias are a classic chemically defended
clade of plants with toxic cardenolides (cardiac glycosides) and pressurized latex employed as
anti-herbivore weapons. Here we combine a comparative approach to investigate broadscale
patterns in allocation to root vs. shoot defenses across species with a species-specific
experimental approach to identify the consequences of defense allocational shifts on a
specialist herbivore. Our results show phylogenetic conservatism for inducibility of shoot
cardenolides by an aboveground herbivore, with only four closely related tropical species
showing significant induction; the eight temperate species examined were not inducible.
Allocation to root and shoot cardenolides was positively correlated across species, and this
relationship was maintained after accounting for phylogenetic nonindependence. In contrast
to long-standing theoretical predictions, we found no evidence for a trade-off between

  

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

 

Collections: Environmental Sciences and Ecology