TABLE 5.

Evaluation of different models in creating correlation matrices similar to average empirical matrices^a

Distribution type	Value for indicated threshold and group
	1%		4%	0.1%
	OTU	Sequence	OTU	OTU
Uniform plus six normal curvesb	0.98	0.92	>0.99	0.99
Two-phase exponential decayc	0.91	0.68	>0.99	0.99
Powerd	0.80	0.70	ND	ND
Uniforme	0.65	0.54	ND	ND
Contrastf	**	**	**	*

^aValues shown are Mantel statistics which reflect the congruence of (i) the average correlation matrix created using empirical TRF size distributions with (ii) the correlation matrix created using the model shown, performed over the same range in S_T (1,200 for OTU sampling and 4,000 for sequence sampling). ND, not determined.

^bDistribution described in text.

^cWithin the analyzed size range (50 to 600 bp), TRF size distribution followed y= a₁ exp(−k₁ × x) + a₂ exp(−k₂ × x) + b, where x is TRF size minus 49. Based on fitted empirical data, a₁ was allowed to vary from 0 to 14, a₂ from 17 to 111, k₁ from 0.0025 to 0.03373, k₂ from 0.093 to 0.7513, and b from 0.12 to 1. The probability that a species had TRF in the analyzed size range varied between 0.2 and 0.34.

^dSame as two-phase exponential-decay distribution, except that TRF size distribution followed y = ax^b; a varied from 90 to 120, and b varied from −0.87 to −1.

^eThe species was assigned a random TRF size between 1 and 1,000 bp; the analyzed size range remained 50 to 600 bp.

^fSignificance of difference between the uniform-plus-six-normal-curve and two-phase exponential-decay distributions in terms of absolute deviations from OTU sampling and sequence sampling correlations (two-tailed pairwise t test). **, P < 0.01; *, P < 0.1. The mean absolute deviation was smaller for the uniform-plus-six-normal-curve distribution for each comparison.