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Table 1 Effect of herbivore identity, feeding intensity and their interaction on black poplar volatile emission

From: The timing of herbivore-induced volatile emission in black poplar (Populus nigra) and the influence of herbivore age and identity affect the value of individual volatiles as cues for herbivore enemies

Compound   Interaction (feeding intensity x Herbivore treatment) Herbivory treatment Feeding intensity
  Variance structure Likelihood ratio p. value Likelihood ratio p. value Likelihood ratio p. value
Monoterpenes        
α-Pinene (cyclic) 7 0.906 0.824 15.227 0.002** 15.393 <0.001***
Camphene (cyclic) 2 0.999 0.802 8.246 0.038* 8.883 0.003**
Myrcene (cyclic) 4 0.642 0.887 8.364 0.04* 7.533 0.006**
Borneol (cyclic) 2 0.779 0.855 6.925 0.074 9.052 0.003**
(Z)-Ocimene (acyclic) 8 3.951 0.267 7.286 0.063 8.424 0.004**
(E)-β-Ocimene (acyclic) 4 1.384 0.709 9.797 0.020* 14.036 <0.001***
Linalool (acyclic) 2 1.441 0.696 2.456 0.483 11.012 <0.001***
Homoterpene        
DMNT 8 7.797 0.051 3.786 0.286 0.444 0.505
Sesquiterpenes        
(E)-β-Caryophyllene 2 0.667 0.881 11.371 0.01* 4.334 0.037*
α-Humulene 2 1.526 0.676 9.014 0.029* 1.676 0.196
Nerolidol 4 6.410 0.093 10.387 0.016* 12.891 <0.001***
Green leaf volatiles        
(Z)-3-Hexenyl acetate 2 0.656 0.884 6.067 0.108 6.454 0.011*
(Z)-3-Hexenol 1 2.284 0.516 16.015 0.001** 0.138 0.71
N-containing comp.        
2-Methylbutyraldoxime 7 0.522 0.914 10.821 0.013* 4.454 0.035*
3-Methylbutyraldoxime 4 0.536 0.911 14.950 0.002** 10.335 0.001**
Benzyl cyanide 3 2.723 0.466 10.852 0.013* 9.464 0.002**
Indol 3 2.136 0.545 9.688 0.021* 1.537 0.215
Aromatic compounds        
Salicyl aldehyde 8 8.734 0.033* 13.706 0.003** 0.535 0.464
Benzyl alcohol 4 4.867 0.182 4.624 0.202 6.770 0.386
Benzene ethanol 4 8.003 0.046* 7.629 0.054 0.703 0.402
  1. For each parameter the F and p values are given. Asterisks indicate significant differences, p < 0.001 = ***, p < 0.01 = **, p < 0.05 = *, no asterisk = not significant. Compounds are grouped according to their chemical classes, the second column shows the variance structure with the lowest Akaike Information Criterion (AIC), which was used in the Generalized Least Square model (GLS). Variance structures tested were as follows: 1. varFixed variance for feeding intensity, 2. varIdent variance for herbivory treatment, 3. varPower variance for herbivory treatment, 4. varExp variance for feeding intensity, 5. varConstPower for feeding intensity, 6. varConstPower for feeding intensity and herbivory treatment, 7. Combined variance (varIdent for herbivory treatment, varFixed for feeding intensity) and 8. Combined variance (varIdent for herbivory treatment, varExp for feeding intensity). A detailed description of the variance structures is given by [80].