Table 2.

Ka/Ks values for each new Nosema/Vairimorpha RPB1 sequence, compared to that of V. necatrix.

Species pair	Non-synonymous positions	Non-synonymous differences	Ka	Synonymous positions	Synonymous differences	Ks	Ka/Ks
N. apis:V. necatrix	1437.58	229.25	0.1793	383.42	211.75	0.9999	0.1793
N. bombycis:V. necatrix	1434.67	259.58	0.2071	386.33	247.42	1.4426	0.1436
N. empoascae:V. necatrix	1427.75	250.17	0.1996	393.25	291.83	3.4155	0.0584
N. granulosis:V. necatrix	1427.58	262.58	0.2110	393.42	285.42	2.5655	0.0822
N. trichoplusiae:V. necatrix	1434.00	260.83	0.2083	387.00	249.17	1.4664	0.1420
V. cheracis:V. necatrix	1421.33	278.25	0.2269	399.67	372.75	-	-
V. cheracis:N. empoascae	1409.42	143.17	0.1091	411.58	283.83	1.8895	0.0577

Values of Ka/Ks considerably lower than 1 indicate relatively low levels of sequence polymorphism at non-synonymous sites, an indicator of strong purifying selection and hence of gene activity. The sequence of V. cheracis is too divergent from that of V. necatrix for Ka/Ks cannot be calculated, so an additional comparison is performed between V. cheracis and N. empoascae.