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Table 2 Summary from the linear mixed models exploring the role of social rank explaining variation in sperm design and total sperm length after 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 0.33 ± 0.79    102.18 ± 0.73   
Rank   0.80 (3,33.4) 0.50   1.01 (3,33.4) 0.40
 Subordinate 1 −0.77 ± 1.11    −0.24 ± 1.04   
 Subordinate 2 −0.58 ± 1.09    −0.48 ± 1.02   
 Subordinate 3 0.77 ± 1.09    1.14 ± 1.02   
Centred body mass −0.59 ± 0.51 1.68 (1,44.3) 0.20 −0.49 ± 0.47 2.96 (1,44.3) 0.09
Centred tarsus length 1.28 ± 1.11 2.85 (1,42.6) 0.10 1.99 ± 1.04 1.74 (1,42.6) 0.19
Rank x Centred body mass   2.86 (3,42.9) 0.048   2.88 (3,42.9) 0.047
 Subordinate 1 1.11 ± 1.08    0.75 ± 1.01   
 Subordinate 2 2.67 ± 0.9    2.26 ± 0.84   
 Subordinate 3 1.27 ± 0.76    1.64 ± 0.71   
Rank x Centred tarsus length   2.82 (3,43.2) 0.05   3.57 (3,43.2) 0.022
 Subordinate 1 −1.99 ± 1.62    −3.09 ± 1.51   
 Subordinate 2 −5.23 ± 2.14    −4.47 ± 1.99   
 Subordinate 3 − 4.12 ± 1.59    − 4.83 ± 1.49   
  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)