The roles of abiotic factors, dispersal, and species interactions in structuring stream assemblages of black flies (Diptera: Simuliidae)

McCreadie, John W; Adler, Peter H

doi:10.1186/2046-9063-8-14

Table 1 PCA and subsequent correlation analysis between stream variables and derived principal components (PCs)

From: The roles of abiotic factors, dispersal, and species interactions in structuring stream assemblages of black flies (Diptera: Simuliidae)

Stream variables				Principal components ²
	Min.	Max.	Mean ( ± SE)	PC₁	PC₂	PC₃
Spring
Temperature (°C)	7.0	16.0	11.1 ± 0.30	-0.505 **	-0.363 *	-0.118
pH	5.6	7.5	6.5 ± 0.05	0.554 **	-0.383 *	0.325
% Dissolved Oxygen	93.2	115.4	102 ± 0.66	-0.131	-0.710 **	0.130
Conductivity (°S cm^-1, 25°C)	16	152	40 ± 3.2	0.483 **	-0.073	0.377 **
Depth (m)	0.08	1.88	0.40 ± 0.047	0.783 **	0.258	-0.250
Velocity (m/s)	0.09	0.87	0.40 ± 0.024	-0.020	-0.816 **	-0.139
Width (m)	0.5	20.0	6.6 ± 0.67	0.807 **	-0.005	-0.272
Discharge (m³/s)	0.01	17.9	1.5 ± 0.40	0.861 **	-0.089	-0.280
Seston (mg/L)	2.0	74.0	14.0 ± 0.30	0.144	-0.623 **	0.151
Streambed-particle size ¹	1.0	6.0	2.0 ± 0.26	-0.308	-0.788 **	-0.123
Riparian vegetation ¹	1.0	3.0	2.1 ± 0.14	-0.347 *	-0.087	-0.736 **
Canopy cover ¹	1.0	3.0	1.6 ± 0.09	-0.418 *	0.151	-0.655 **
% variance explained in PCA
Proportion				24.9	21.8	15.0
Cumulative				24.9	46.8	61.7
Summer
Temperature (° C)	13.0	29.0	20.0 ± 0.49	0.514 **	-0.560 **	0.054
pH	5.80	7.9	7.1 ± 0.06	0.085	0.239	0.782 **
% Dissolved Oxygen	78.8	106.7	93.25 ± 0.93	-0.021	0.650 **	-0.433 *
Conductivity (°S cm^-1, 25°C)	10	235	73 ± 7.46	0.303	-0.137	0.897 **
Depth (m)	0.03	0.73	0.18 ± 0.029	0.873 **	0.003	-0.124
Velocity (m/s)	0.02	0.67	0.31 ± 0.018	0.424 *	0.616 **	-0.296
Width (m)	0.30	36.00	7.5 ± 1.20	0.871**	0.162	0.219
Discharge (m³/s)	0.01	9.38	0.73 ± 0.209	0.889 **	0.236	0.019
Seston (mg/L)	2.8	50.0	14.6 ± 0.49	0.237	-0.079	0.091
Streambed-particle size ¹	1.0	6	2.0 ± 0.24	-0.124	0.892 **	-0.098
Riparian vegetation ¹	1.0	3	2.3 ± 0.13	-0.121	0.386 *	0.076
Canopy cover ¹	1.0	3.	2.0 ± 0.15	-0.473 **	0.220	0.056
% variance explained in PCA
Proportion				26.4	20.3	15.8
Cumulative				26.4	46.8	62.6

¹Dominant streambed-particle size (mud = 1, sand = 2, small stones = 3, rubble = 4, boulders = 5, bedrock = 6), riparian vegetation (open = 1, brush = 2, forest = 3) and canopy cover (none = 1, partial = 2, complete = 3) are ranked variables, with medians presented.
²Significant correlation at * P < 0.01, ** P < 0.001.

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