Table 1 Linear mixed model analysis to test for inbreeding depression for vegetative performance for six outcrossing and six selfing populations of A. lyrata

From: Sibling competition does not magnify inbreeding depression in North American Arabidopsis lyrata

Explanatory variables (fixed and random effects)

dfnum

4-week old plants

11-week old plants

Belowground biomass (Gaussian, square root, n = 347)

Aboveground biomass (Gaussian, square root, n = 350)

Aboveground biomass (Gaussian, square root, n = 359)

adfden

F

P

adfden

F

P

adfden

F

P

Fixed

Cross type (CT)

1

285.4

12.5

<0.001

284.4

22.6

<0.001

298.1

12.3

0.001

Mating system (MS)

1

11.2

0.59

0.46

10.7

0.23

0.64

14.2

<0.001

0.99

Competition (C)

1

274.7

20.1

<0.001

274.3

3.73

0.055

298.7

183.0

<0.001

CT: MS

1

285.4

0.05

0.82

284.4

1.71

0.19

298.1

2.36

0.13

CT: C

1

282.6

0.86

0.36

282.1

2.13

0.15

297.1

0.042

0.84

MS: C

1

274.7

1.74

0.19

274.3

0.52

0.47

298.7

0.027

0.87

CT:MS:C

1

282.6

<0.001

0.99

282.1

0.17

0.68

297.1

0.14

0.71

Random

 

SD

SD

SD

Population

1

0.186

0.025

0.149

Mother

1

0.307

0.033

0.159

Residual

 

0.678

0.065

0.591

  

dfres  =  336

dfres  =  339

dfres  =  348

  1. Cross type represents inbreeding depression in the model (alone or in interaction with competition and/or mating system). Proxies for vegetative performance were belowground biomass and aboveground biomass in 4-week old plants, and aboveground biomass in 11-week old plants. The model error distribution, any applied transformations and sample sizes are indicated in brackets for each trait. For all traits, the model fixed part included cross type (self vs. cross), mating system (outcrossing vs. selfing) and competition (with vs. without), and all two-way and three-way interactions. The random effects included population (nested in mating system) and mother plant (nested in population). Significant values are marked in bold. Significant effects of cross type (as main effect or in interaction) indicate significant inbreeding depression
  2. dfnum : numerator degrees of freedom, dfden : denominator degrees of freedom
  3. aSignificance tests are based on Satterthwaite’s method to adjust dfden, as implemented in the anova command in the package lmerTest (v3.1–0)
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