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Table 5 Model selection table for different models testing the relationship between male competitive ability and fertilization success (sperm traits)

From: Competitive males have higher quality sperm in a monogamous social bee

Selection episode

N. obs

Response

Starting model

Fixed effect removed

Degrees of freedom

χ2

P-value

Colony - Aggregation

47

Sperm viability

sampling site*days in incubator

interaction

1

0.05

0.82

sampling site + days in incubator

sampling site

1

0.29

0.59

sampling site + days in incubator

days in incubator

1

0.004

0.95

sampling site

sampling site

1

1.82

0.18

days in incubator

days in incubator

1

1.54

0.21

1070

Sperm length

sampling site

sampling site

1

0.01

0.91

107

Sperm length variation

sampling site

sampling site

1

0.12

0.73

Persistence time in the aggregation

60

Sperm viability

days at aggregation

days at aggregation

2

7.28

0.03

90

Sperm number

days at aggregation

days at aggregation

2

3.77

0.15

609

Sperm length

days at aggregation

days at aggregation

2

12.70

<0.01

61

Sperm length variation

days at aggregation

days at aggregation

2

16.07

<0.001

  1. The p-values and degrees of freedom refer to Likelihood Ratio Tests (using a χ2 test statistic), in which the full model was compared to a reduced model without each of the predictor variables. Parameters estimates of best models are presented in Table 5