TABLE 3.

Cooccurrence indices computed for incidence matrices from all sampling events or individual sites relative to null matrices using EcoSim 7.72a

SamplesC-scoreC-boardCombo
ObservedMean nullVariance nullP (observed ≤ null)P (observed ≥ null)SESObservedMean nullVariance nullP (observed ≤ null)P (observed ≥ null)SESObservedMean nullVariance nullP (observed ≤ null)P (observed ≥ null)SES
All19.419.10.0150.9810.019b2.451,1921,1372500.9990.001b3.4769.075.24.920.000b1.000−2.80
Old Salinas River4.043.810.0140.9600.044b1.9466.064.324.10.6760.4040.3515.014.80.720.7730.6570.21
Pescadero Creek9.359.070.0160.0980.024b2.1679.073.015.10.9470.0851.5420.020.40.440.5440.903−0.53
San Lorenzo River3.223.230.0070.4970.524−0.1487.071.045.30.9930.012b2.3814.015.00.660.2630.966−1.21
Waddell Creek2.401.770.0260.9980.002b3.9216.07.717.550.9960.028b3.028.009.190.470.1450.994−1.74
  • a See reference 14. C-board is the number of genotype pairs never occurring in the same sample, Combo is the number of unique genotype cooccurrences between sites, and C-score is the average number of “checkerboard” units between samples. SES, standardized effect score. Kirby Park, Lagunitas Creek, Moss Landing Harbor, San Pedro Creek, and Soquel Creek were excluded due to small numbers of nonsingleton genotypes (<3).

  • b There was significant deviation in the indices (P < 0.05) from values expected by chance (null distribution).