TABLE 3.

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

Samples	C-score						C-board						Combo
	Observed	Mean null	Variance null	P (observed ≤ null)	P (observed ≥ null)	SES	Observed	Mean null	Variance null	P (observed ≤ null)	P (observed ≥ null)	SES	Observed	Mean null	Variance null	P (observed ≤ null)	P (observed ≥ null)	SES
All	19.4	19.1	0.015	0.981	0.019b	2.45	1,192	1,137	250	0.999	0.001b	3.47	69.0	75.2	4.92	0.000b	1.000	−2.80
Old Salinas River	4.04	3.81	0.014	0.960	0.044b	1.94	66.0	64.3	24.1	0.676	0.404	0.35	15.0	14.8	0.72	0.773	0.657	0.21
Pescadero Creek	9.35	9.07	0.016	0.098	0.024b	2.16	79.0	73.0	15.1	0.947	0.085	1.54	20.0	20.4	0.44	0.544	0.903	−0.53
San Lorenzo River	3.22	3.23	0.007	0.497	0.524	−0.14	87.0	71.0	45.3	0.993	0.012b	2.38	14.0	15.0	0.66	0.263	0.966	−1.21
Waddell Creek	2.40	1.77	0.026	0.998	0.002b	3.92	16.0	7.71	7.55	0.996	0.028b	3.02	8.00	9.19	0.47	0.145	0.994	−1.74

^aSee 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).

^bThere was significant deviation in the indices (P < 0.05) from values expected by chance (null distribution).