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Table 1 Summary from the linear mixed models exploring the role of social rank explaining variation in sperm design and total sperm length before manipulating the social status

From: Is sperm morphology functionally related to sperm swimming ability? A case study in a wild passerine bird with male hierarchies

  Sperm design Total sperm length
Fixed effects Slope ± SD F (df1, df2) p Slope ± SD F (df1, df2) p
Intercept −0.79 ± 0.86    102.28 ± 0.79   
Rank   1.72 (3,34) 0.18   0.88 (3,33.9) 0.46
 Subordinate 1 1.7 ± 1.23    1.35 ± 1.12   
 Subordinate 2 1.43 ± 1.21    1.09 ± 1.1   
 Subordinate 3 −0.66 ± 1.21    −0.08 ± 1.1   
Centred body mass 0.99 ± 0.86 4.00 (1,44.6) 0.052 0.77 ± 0.79 4.82 (1,43.9) 0.033
Centred tarsus length 1.15 ± 1.71 1.10 (1,46.4) 0.30 −0.14 ± 1.57 2.70 (1,46.8) 0.11
Rank x Centred body mass   1.70 (3,46.4) 0.18   1.25 (3,46.6) 0.30
 Subordinate 1 0.65 ± 1.2    0.33 ± 1.1   
 Subordinate 2 −1.76 ± 1.16    − 1.14 ± 1.07   
 Subordinate 3 0.31 ± 1.09    0.75 ± 1.01   
Rank x Centred tarsus length   0.78 (3,45.5) 0.51   0.46 (3,45.5) 0.71
 Subordinate 1 −3.96 ± 2.52    −2.11 ± 2.31   
 Subordinate 2 −2.07 ± 2.03    −0.47 ± 1.86   
 Subordinate 3 −1.83 ± 2.21    − 1.82 ± 2.04   
  1. Estimates from linear mixed models, and F and p values correspond to an ANOVA using a Kenward-Roger approximation to the degrees of freedom. Contrasts are done against the means of dominant males. Bold p-values are significant (alpha = 0.05)