Table 1.

Diversity (P_n/P_s) and divergence (D_n/D_s) information for NAD biosynthetic and NAD degrading genes in four species. A test of positive selection (McDonald Kreitman (MK) test) was conducted, which contrasts the level of P_n/P_s and D_n/D_s.

Species		NAD biosynthesis		NAD degradation
Homo sapiens
	Pn/Ps	0.28	≈	0.45
	Dn/Ds	0.26	<	0.39
	MK-test	n.s.		n.s.
Mus musculus
	Pn/Ps	0.10	≈	0.12
	Dn/Ds	0.32	>	0.26
	MK-test	**		**
Drosophila melanogaster
	Pn/Ps	0.03	<	0.06
	Dn/Ds	0.06	≈	0.06
	MK-test	*		n.s.
Arabidopsis thaliana
	Pn/Ps	0.21	≈	0.24
	Dn/Ds	0.12	<	0.16
	MK-test	n.s.		n.s.

n.s. – not significant; <, > signs indicate significant differences between the two enzyme groups using a permutation test; ≈ indicates no significant difference.

^*P < 0.05.

^**P < 0.001.