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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].