Table 2.

Selective pressure analyses of the mitochondrial OXPHOS genes of asteroids.

Branch-specific models
Models	lnL	Parameter estimates	Model compared	2ΔlnL	p-values
Free-ratio model (M1)	− 204017.5186		M1 versus M0	− 1823.43544**	0.0000
Two-ratio model (M2)	− 204929.2363	ω0 = 0.09129 ω1 = 0.09158	M2 versus M0	0.00565	0.9402
One-ratio model (M0)	− 204929.2391	ω = 0.09132

Branch	Branch-sits models
	Species	Gene	Positively selected sites
Foreground-lineage I	C. papposus	atp8	45 K 0.966*
		nad2	229 F 0.957*
			279 G 0.960*
		nad6	110 W 0.997**
			156 S 0.973*
Foreground-lineage II	S. yapensis + Cheiraster sp.	nad2	45 C 0.960*
		nad4	375 K 0.957*
Foreground-lineage III	Paulasterias sp.	nad2	158 G 0.974*
			201 G 0.961*
		nad3	20 A 0.970*
		nad4	417 K 0.961*
Foreground-lineage IV	F. benthophila + Brisinga sp.	cox3	145 A 0.979*
		cytb	324 T 0.953*
		nad1	88 C 0.962*
			277 S 0.972*
		nad2	42 P 0.958*
			196 Y 0.965*
			280 G 0.960*
		nad4	11 T 0.976*
			78 L 0.981*
			101 L 0.984*
			188 S 0.986*
			254 S 0.983*
			453 K 0.976*
		nad4l	42 T 0.987*
			81 S 0.989*
Foreground-lineage V	Z. ophiactis	nad2	21 V 0.952*
			146 V 0.972*
			213 S 0.989*
		nad4l	41 N 0.992**
Foreground-lineage VI	A. papyraceus	nad2	281 L 0.957*
		nad4	45 H 0.985*
			362 L 0.982*
			405 A 0.974*

* 0.001 < p < 0.01 ** p < 0.001