The influence of gene-environment interactions on GHR and IGF-1 expression and their association with growth in brook charr, Salvelinus fontinalis (Mitchill)

Table 9 Model selection for absolute growth using a backwards step-wise procedure.

	Absolute growth
Model	Log likelihood	Test	P
Growth ~Env + Sex + EBV·Env + EBV·Sex +Env·Sex +EBV·Env·Sex (1)	-107.460
~Env + Sex + EBV·Env + EBV·Sex +Env·Sex (2)	-108.443	1 vs. 2	0.169
~Env + Sex + EBV·Env + EBV·Sex (3)	-108.499	2 vs. 3	0.737
~Env + Sex + EBV·Env (4)	-108.607	3 vs. 4	0.643
~Env + Sex (5)	-112.465	4 vs. 5	0.021

Progressively simpler models are subsequently defined by removing terms from previous models beginning with interaction effects (e.g. 1 vs. 2). Nested models were tested evaluated using likelihood ratio tests to select the most parsimonious model. The reported p-values correspond to results of the likelihood ratio tests wherein a value greater than the nominal level of significance (α = 0.05) indicates that removal of the model term does not increase model deviance significantly. The final, parsimonious model that was selected is indicated in bold characters (Env = environment, EBV = EBV group).

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