Table 3.

Results of ANOVA analyses of effect of male category and body mass on male fertility

Response variable	Explanatory variable	df numerator	df denominator	F	p-value
Cauda sperm	Male category	2	25.19	1.12	0.34
	Body mass	1	39.04	4.47	0.04
Testis mass	Male category	4	74.75	210.29	< 10−15
	Body mass	1	103.29	15.81	< 0.001
Epididymis mass	Male category	4	72.16	63.10	< 10−15
	Body mass	1	103.00	23.80	< 10−5
Seminal vesicle and coagulating gland	Male category	4	73.13	2.63	0.04
	Body mass	1	103.69	45.79	< 10−9
Preputial gland	Male category	4	72.13	2.01	0.10
	Body mass	1	93.78	22.93	< 10−5

Parent pair was used as a random effect to correct for the inclusion of siblings in the dataset. For all response variables except cauda sperm, male categories included the CHBU parental race, the CHHN parental race, F₁ between CHBU and CHHN, offspring from backcrosses to CHHN with 2n = 23, and offspring from backcrosses to CHHN with 2n = 24. In the model for cauda sperm, only male categories with sperm were tested (CHBU, CHHN, and offspring from backcrosses to CHHN with 2n = 24, see text)