Effects of carbon dioxide on the searching behaviour of the root-feeding clover weevil Sitona lepidus (Coleoptera: Curculionidae)

Scott N. Johnson, Xiaoxian Zhang, John W. Crawford, Peter J. Gregory, N. J Hix, Steve C. Jarvis, Philip J. Murray, Iain M. Young

Research output: Contribution to journalArticle

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Abstract

The respiratory emission of CO2 from roots is frequently proposed as an attractant that allows soil-dwelling insects to locate host plant roots, but this role has recently become less certain. CO2 is emitted from many sources other than roots, so does not necessarily indicate the presence of host plants, and because of the high density of roots in the upper soil layers, spatial gradients may not always be perceptible by soil-dwelling insects. The role of CO2 in host location was investigated using the clover root weevil Sitona lepidus Gyllenhall and its host plant white clover (Trifolium repens L.) as a model system. Rhizochamber experiments showed that CO2 concentrations were approximately 1000 ppm around the roots of white clover, but significantly decreased with increasing distance from roots. In behavioural experiments, no evidence was found for any attraction by S. lepidus larvae to point emissions of CO2, regardless of emission rates. Fewer than 15% of larvae were attracted to point emissions of CO2, compared with a control response of 17%. However, fractal analysis of movement paths in constant CO2 concentrations demonstrated that searching by S. lepidus larvae significantly intensified when they experienced CO2 concentrations similar to those found around the roots of white clover (i.e. 1000 ppm). It is suggested that respiratory emissions of CO2 may act as a ‘search trigger’ for S. lepidus, whereby it induces larvae to search a smaller area more intensively, in order to detect location cues that are more specific to their host plant.
Original languageEnglish
Pages (from-to)361-366
Number of pages6
JournalBulletin of Entomological Research
Volume96
Issue number4
DOIs
StatePublished - 2006

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Appetitive Behavior
Weevils
Medicago
Beetles
Carbon Dioxide
Larva
Sitona lepidus
Trifolium repens
host plants
larvae
Soil
Curculionidae
soil
Insects
insects
Trifolium
Fractals
Plant Roots
Cues
searching behavior

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Johnson, S. N., Zhang, X., Crawford, J. W., Gregory, P. J., Hix, N. J., Jarvis, S. C., ... Young, I. M. (2006). Effects of carbon dioxide on the searching behaviour of the root-feeding clover weevil Sitona lepidus (Coleoptera: Curculionidae). Bulletin of Entomological Research, 96(4), 361-366 . DOI: 10.1079/BER2006436

Johnson, Scott N.; Zhang, Xiaoxian; Crawford, John W.; Gregory, Peter J.; Hix, N. J; Jarvis, Steve C.; Murray, Philip J.; Young, Iain M. / Effects of carbon dioxide on the searching behaviour of the root-feeding clover weevil Sitona lepidus (Coleoptera: Curculionidae).

In: Bulletin of Entomological Research, Vol. 96, No. 4, 2006, p. 361-366 .

Research output: Contribution to journalArticle

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abstract = "The respiratory emission of CO2 from roots is frequently proposed as an attractant that allows soil-dwelling insects to locate host plant roots, but this role has recently become less certain. CO2 is emitted from many sources other than roots, so does not necessarily indicate the presence of host plants, and because of the high density of roots in the upper soil layers, spatial gradients may not always be perceptible by soil-dwelling insects. The role of CO2 in host location was investigated using the clover root weevil Sitona lepidus Gyllenhall and its host plant white clover (Trifolium repens L.) as a model system. Rhizochamber experiments showed that CO2 concentrations were approximately 1000 ppm around the roots of white clover, but significantly decreased with increasing distance from roots. In behavioural experiments, no evidence was found for any attraction by S. lepidus larvae to point emissions of CO2, regardless of emission rates. Fewer than 15% of larvae were attracted to point emissions of CO2, compared with a control response of 17%. However, fractal analysis of movement paths in constant CO2 concentrations demonstrated that searching by S. lepidus larvae significantly intensified when they experienced CO2 concentrations similar to those found around the roots of white clover (i.e. 1000 ppm). It is suggested that respiratory emissions of CO2 may act as a ‘search trigger’ for S. lepidus, whereby it induces larvae to search a smaller area more intensively, in order to detect location cues that are more specific to their host plant.",
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Johnson, SN, Zhang, X, Crawford, JW, Gregory, PJ, Hix, NJ, Jarvis, SC, Murray, PJ & Young, IM 2006, 'Effects of carbon dioxide on the searching behaviour of the root-feeding clover weevil Sitona lepidus (Coleoptera: Curculionidae)' Bulletin of Entomological Research, vol 96, no. 4, pp. 361-366 . DOI: 10.1079/BER2006436

Effects of carbon dioxide on the searching behaviour of the root-feeding clover weevil Sitona lepidus (Coleoptera: Curculionidae). / Johnson, Scott N.; Zhang, Xiaoxian; Crawford, John W.; Gregory, Peter J.; Hix, N. J; Jarvis, Steve C.; Murray, Philip J.; Young, Iain M.

In: Bulletin of Entomological Research, Vol. 96, No. 4, 2006, p. 361-366 .

Research output: Contribution to journalArticle

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AU - Johnson,Scott N.

AU - Zhang,Xiaoxian

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AU - Gregory,Peter J.

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AU - Young,Iain M.

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AB - The respiratory emission of CO2 from roots is frequently proposed as an attractant that allows soil-dwelling insects to locate host plant roots, but this role has recently become less certain. CO2 is emitted from many sources other than roots, so does not necessarily indicate the presence of host plants, and because of the high density of roots in the upper soil layers, spatial gradients may not always be perceptible by soil-dwelling insects. The role of CO2 in host location was investigated using the clover root weevil Sitona lepidus Gyllenhall and its host plant white clover (Trifolium repens L.) as a model system. Rhizochamber experiments showed that CO2 concentrations were approximately 1000 ppm around the roots of white clover, but significantly decreased with increasing distance from roots. In behavioural experiments, no evidence was found for any attraction by S. lepidus larvae to point emissions of CO2, regardless of emission rates. Fewer than 15% of larvae were attracted to point emissions of CO2, compared with a control response of 17%. However, fractal analysis of movement paths in constant CO2 concentrations demonstrated that searching by S. lepidus larvae significantly intensified when they experienced CO2 concentrations similar to those found around the roots of white clover (i.e. 1000 ppm). It is suggested that respiratory emissions of CO2 may act as a ‘search trigger’ for S. lepidus, whereby it induces larvae to search a smaller area more intensively, in order to detect location cues that are more specific to their host plant.

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