The baculum affects paternity success of first but not second males in house mouse sperm competition

Table 1 Results of beta-binomial mixed models for effects of baculum size (length, shaft width and base width) or morphometrics (relative warps 1 & 2 (RW)) on fertilization success of the first male relative to the second male (P₁), including body mass and genotype as covariates

Model	Variable	Estimate	Std. error	z value	p-value	p-adj
Baculum size resid. df = 27	Intercept	1.38	0.43	3.19	0.001	0.007
	Length M1	0.17	0.38	0.44	0.660	0.724
	Shaft width M1	1.66	0.53	3.12	0.002	0.007
	Base width M1	0.32	0.28	1.11	0.267	0.367
	Length M2	− 0.53	0.37	− 1.42	0.154	0.243
	Shaft width M2	− 0.62	0.42	− 1.47	0.141	0.243
	Base width M2	− 0.10	0.28	− 0.35	0.7244	0.724
	Body mass M1	0.37	0.36	1.03	0.303	0.371
	Body mass M2	0.91	0.36	2.53	0.011	0.031
	Genotype M1 and M2 (+ /t)	− 2.40	0.58	4.15	< 0.001	< 0.001
	Plug removal (removed)	− 0.98	0.54863	− 1.796	0.07257	0.160
Baculum shape (morphometrics) resid. df = 25	Intercept	1.02	0.47	2.17	0.030	0.166
	log₁₀ Centroid size M1	0.15	0.37	0.41	0.684	0.912
	RW1 M1	0.66	0.39	1.71	0.088	0.322
	RW2 M1	− 0.11	0.35	− 0.31	0.754	0.912
	log₁₀ Centroid size M2	0.007	0.52	0.01	0.989	0.989
	RW1 M2	− 0.19	0.37	− 0.53	0.596	0.912
	RW2 M2	− 0.29	0.32	− 0.91	0.361	0.795
	Body mass M1	− 0.15	0.40	− 0.389	0.699	0.912
	Body mass M2	0.51	0.46	1.10	0.271	0.746
	Genotype M1 and M2 (+ /t)	− 2.77	0.83	− 3.35	< 0.001	0.009
	Plug removal (removed)	− 0.12	0.54	− 0.22	0.829	0.912

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