TABLE 5.

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

Distribution typeValue for indicated threshold and group
1%4%0.1%
OTUSequenceOTUOTU
Uniform plus six normal curvesb0.980.92>0.990.99
Two-phase exponential decayc0.910.68>0.990.99
Powerd0.800.70NDND
Uniforme0.650.54NDND
Contrastf*******
  • a Values 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 ST (1,200 for OTU sampling and 4,000 for sequence sampling). ND, not determined.

  • b Distribution described in text.

  • c Within 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.

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

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

  • f Significance 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.