Table 2. Four nested Generalized Linear Models of species density of native ants.

	Abundance of native ants		+ Number of pitfall traps per site		+ P. chinensis abundance		+ Saturation of P. chinensis
	Parameter estimates	Effect test	Parameter estimates	Effect test	Parameter estimates	Effect test	Parameter estimates	Effect test
Intercept	2.06	P<0.0001	2.01	P<0.0001	1.99	P<0.0001	1.96	P<0.0001
Abundance of native ants	2.1×10−3	P<0.0001	2.1×10−3	P<0.0001	1.4×10−3	P = 0.0091	1.2×10−3	P = 0.045
Number of pitfall trap per site	Not included	Not included	3.4×10−3	Not significant	1.8×10−2	Not significant	2.5×10−2	Not significant
P. chinensis abundance	Not included	Not included	Not included	Not included	−5.3×10−4	P = 0.0021	−4.5×10−4	P = 0.016
Saturation of P. chinensis	Not included	Not included	Not included	Not included	Not included	Not included	−9.2×10−3	Not significant
−Log likelihood	10.67		12.20		15.43		15.85

Models are ordered according to increasing complexity, from left to right. The first model includes only the abundance of native ants. “+number of pitfall traps per site” includes the abundance of native ants as well as the number of pitfall traps collected per site. “+P. chinensis abundance” model includes the abundance of native ants, the number of pitfall traps per site and the total abundance of P. chinensis per site. “+saturation of P. chinensis” model includes the effect of the number of pitfall traps collected where P. chinensis was present. Only the effect of the abundance of native ants is positively associated with native species density, while only P. chinensis abundance is negatively associated with native species density. All four models are exponentials of the form species density = e ^{Σ parameter i*value j}.