Table 3. AIC and p values resulting from the application of the linear GLM and non-linear GAM models to each individual set of data to investigate the correlation between stable isotope values and age.

		GLM		GAM
	ID	AIC	p	AIC	p
δ15N	A	11.47	<0.001	11.47	<0.001
	B	24.46	0.61	24.46	0.61
	C	15.28	<0.01	15.28	<0.01
	D	12.02	<0.05	12.02	<0.05
	E	7.01	<0.001	6.86●	<0.001
	F	4.39	<0.05	4.39	<0.05
	G	9.40	<0.001	9.40	<0.001
	H	17.19	0.90	17.19	0.90
	I	31.66	<0.001	18.11●	<0.001
δ13C	A	4.71	<0.05	4.71	<0.05
	B	8.26	0.17	3.47●	0.07
	C	17.88	0.64	-0.83●	<0.001
	D	6.97	0.24	6.97	0.24
	E	9.91	0.53	9.21●	0.69
	F	15.70	0.82	15.70	0.82
	G	15.90	0.13	10.83●	0.62
	H	10.87	<0.05	10.86●	<0.05
	I	-0.09	<0.001	-0.09	<0.001
δ18O	A	8.84	0.98	8.84	0.98
	B	5.92	0.42	5.49●	0.60
	C	4.19	0.64	4.19	0.64
	D	-0.92	0.10	-0.92	0.10
	E	2.09	0.14	2.09	0.14
	F	1.47	0.09	1.47	0.09
	G	5.78	<0.05	5.78	<0.05
	H	5.53	<0.05	5.53	<0.05
	I	1.45	0.69	1.45	0.69

● indicates a lower AIC value resulting from the application of the GAM model than that of GLM.