Red leaf margins indicate increased polygodial content and function as visual signals to reduce herbivory in Pseudowintera colorata.
Red-pigmented leaf margins are common, but their functional significance is unknown. We hypothesized that red leaf margins reduce leaf herbivory by signalling to herbivorous insects the presence of increased chemical defences. Leaves were collected from a natural population of Pseudowintera colorata. Margin size, herbivory damage, anthocyanin content and concentrations of polygodial, a sesquiterpene dialdehyde with antifeedant properties, were quantified. Feeding trials involving larvae of Ctenopseustis obliquana, a generalist herbivore, were conducted on red- and green-margined P. colorata leaves in darkness, or under white, green or red light. Leaves with wider red margins contained higher concentrations of polygodial and anthocyanins, and incurred less natural herbivory. In trials under white light, C. obliquana consumed disproportionately more green- than red-margined leaf laminae. Larvae exhibited no feeding preference when light was manipulated such that leaf colour discrimination was impaired. Red leaf margins provide a reliable and effective visual signal of chemical defence in P. colorata. Ctenopseustis obliquana larvae perceive and respond to the colour of the leaf margins, rather than to olfactory signals. Our study provides direct experimental evidence for aposematic coloration in red leaves.
School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
Luke J
LJ
Cooney
Department of Chemistry, The New Zealand Institute for Plant & Food Research Limited, University of Otago, PO Box 56, Dunedin, New Zealand.
John W
JW
van Klink
Department of Biology, High Point University, University Station 3591, High Point, NC 27262, USA.
Nicole M
NM
Hughes
Department of Chemistry, The New Zealand Institute for Plant & Food Research Limited, University of Otago, PO Box 56, Dunedin, New Zealand.
Nigel B
NB
Perry
Department of Evolutionary Biology and Animal Ecology, Faculty of Biology, University of Freiburg, Hauptstrasse 1, D-79104 Freiburg, Germany.
H Martin
HM
Schaefer
School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
Ignatius J
IJ
Menzies
School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
Kevin S
KS
Gould
D000818:Animals; D000872:Anthocyanins / Q000378:metabolism; D003116:Color; D060434:Herbivory / Q000502:physiology*; D055537:Light Signal Transduction; D009036:Moths / Q000502:physiology; D010058:Oviposition / Q000502:physiology; D010858:Pigmentation / Q000502:physiology*; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000378:metabolism* / Q000469:parasitology; D032425:Pseudowintera / Q000033:anatomy & histology* / Q000469:parasitology*; D012717:Sesquiterpenes / Q000737:chemistry / Q000378:metabolism
D000872:Anthocyanins; D012717:Sesquiterpenes; C034380:polygodial