A1 Vertaisarvioitu alkuperäisartikkeli tieteellisessä lehdessä
Larval parasitism rate increases in herbivore-damaged trees: a field experiment with cyclic birch feeding moths
Tekijät: Klemola T, Ammunét T, Andersson T, Klemola N, Ruohomäki K
Kustantaja: WILEY-BLACKWELL
Julkaisuvuosi: 2012
Journal: Oikos
Tietokannassa oleva lehden nimi: OIKOS
Lehden akronyymi: OIKOS
Numero sarjassa: 10
Vuosikerta: 121
Numero: 10
Aloitussivu: 1525
Lopetussivu: 1531
Sivujen määrä: 7
ISSN: 0030-1299
DOI: https://doi.org/10.1111/j.1600-0706.2011.20096.x
Tiivistelmä
Indirect plant defence mechanisms enhance the effectiveness of natural enemies of herbivores. Herbivore-induced plant volatiles (HIPVs) attract the parasitoids of insect herbivores as shown both in numerous choice tests conducted under laboratory conditions and in relatively few common-garden setups in agro-ecosystems. However, the importance of this indirect defence trait at higher levels of biological organization has yet to be investigated through natural field experiments. Here, we report a field experiment of larval parasitism of two cyclic geometrid defoliators in herbivore-damaged and fairly intact mountain birch Betula pubescens ssp. czerepanovii under natural conditions. Parasitism rates in larvae of the autumnal (Epirrita autumnata) and winter moth (Operophtera brumata) exposed for 30 h on defoliated trees were more than twice as high as those on control trees. This finding indicates that hymenopteran parasitoids were attracted to previously defoliated trees by some cues from the host plants, HIPVs being the most likely candidates. The third trophic level should thus be considered in natural plant herbivore interactions. Furthermore, parasitoids and food resources are key factors in the population regulation of forest insect pests, and indirect plant defences could be important in their interactions. Our research also emphasizes the quality of control treatments in field experiments, since immediate plant responses easily obscure the results as soon as control trees become infested by herbivorous insects.
Indirect plant defence mechanisms enhance the effectiveness of natural enemies of herbivores. Herbivore-induced plant volatiles (HIPVs) attract the parasitoids of insect herbivores as shown both in numerous choice tests conducted under laboratory conditions and in relatively few common-garden setups in agro-ecosystems. However, the importance of this indirect defence trait at higher levels of biological organization has yet to be investigated through natural field experiments. Here, we report a field experiment of larval parasitism of two cyclic geometrid defoliators in herbivore-damaged and fairly intact mountain birch Betula pubescens ssp. czerepanovii under natural conditions. Parasitism rates in larvae of the autumnal (Epirrita autumnata) and winter moth (Operophtera brumata) exposed for 30 h on defoliated trees were more than twice as high as those on control trees. This finding indicates that hymenopteran parasitoids were attracted to previously defoliated trees by some cues from the host plants, HIPVs being the most likely candidates. The third trophic level should thus be considered in natural plant herbivore interactions. Furthermore, parasitoids and food resources are key factors in the population regulation of forest insect pests, and indirect plant defences could be important in their interactions. Our research also emphasizes the quality of control treatments in field experiments, since immediate plant responses easily obscure the results as soon as control trees become infested by herbivorous insects.
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