Table 1. Direct effects of age, mitochondrial and nuclear genetic variation on introgression line for female fecundity (that is, daily rate of egg laying) and fertility, and male ejaculate weight.

Response variable	Fecunditya, n=912					Fertilitya, n=912					Ejaculate weightb, n=615
	Coef	s.e.	χ2	d.f.	P	Coef	s.e.	χ2	d.f.	P	Coef	s.e.	χ2	d.f.	P
Fixed effects
Age	−0.67	0.04	305.0	1	<0.0001	−0.81	0.11	52.5	1	<0.0001			5.8	3	0.1198
Body weight	0.16	0.02	97.0	1	<0.0001	0.01	0.08	0.002	1	0.9636	5.44	0.40	183.6	1	<0.0001
Mating rate	0.04	0.02	6.8	1	0.0091	0.13	0.08	2.9	1	0.0874	—	—	—	—	—
Mitochondrial lineage			7.3	2	0.0266			1.8	2	0.3929			13.9	2	0.0010
Nuclear lineage			6.6	2	0.0373			0.0	2	0.9979			4.6	2	0.0986
Mito × Nuc			12.5	4	0.0141			8.1	4	0.0887			24.8	4	<0.0001
Age × Mito			4.4	2	0.1123			0.3	2	0.8724			31.7	6	<0.0001
Age × Nuc			6.0	2	0.0495			2.4	2	0.2964			24.7	6	<0.0001
Age × Mito × Nuc			10.0	4	0.0422			2.3	4	0.6766			36.4	12	<0.0001
Random effects	Variance (σ2)					Variance (σ2)					Variance (σ2)
Line	2.061 × 10–9					0.00					0.08
ID	2.066 × 10–9					0.40					1.08

Abbreviations: Coef, coefficient; d.f., degrees of freedom; Mito, mitochondrial lineage; Nuc, nuclear lineage. P< 0.05 highlighted in bold.

^aFemale.

^bMale.