Is the Frequency Content of the Calls in North American Treefrogs Limited by Their Larynges?

Table 1

Variance in laryngeal output partitioned among pressure (covariate), individual, and trial within individual, using analyses of covariance. Nine separate analyses address three species and three dependent variables: amplitude, airflow, and frequency.

Variables		Species
Dependent	Independent	H. versicolor		P. streckeri		A. crepitans
			% Var.^a		% Var.^a		% Var.^a
Amplitude	Pressure	513***	43	55***	22	131***	26
	Individual	13***	32	17***	53	12***	48
	Trial (indiv.)	4***	11	1 n.s.	0	3***	11
	Error		14		25		15
Airflow	Pressure	1037***	36	515***	40	214***	20
	Individual	16***	49	3*	30	4**	37
	Trial (indiv.)	11***	11	19***	25	17***	36
	Error		4		5		7
Frequency	Pressure	851***	58	847***	36	420***	23
	Individual	6***	19	7***	46	4**	26
	Trial (indiv.)	6***	16	24***	16	31***	45
	Error		7		2		6

% var. = percent of the variance explained by the independent variable. Significance (not corrected): ***P < 0.001, **P < 0.01, and *P < 0.05; n.s. = not significant.