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

Table 2 BV-STEP routine and partial Mantel tests between species resemblance matrices, stream variables and stream position

BV-STEP routine			Partial mantel correlation coefficients
Best explanatory variables		Correlation¹ coefficient	Stream variable¹	Position²
Spring
All ecoregions	velocity pH, seston, bed	0.4961***	0.3000***	0.3795 ***
Mountain	velocity, O₂, depth, canopy	0.3584 ***	0.3588 ***	- 0.0270
Piedmont	velocity,temperature discharge conductivity	0.5127 **	0.0478	0.6085 ***
Sandhills	temperature, width, discharge	0.1632 *	0.1532	0.2864 **
Summer ⁴
All ecoregions	temperature,conductivity bed	0.5631***	0.4965***	0.1069
Mountain	temperature, width, bed	0.5337***	0.5071***	0.0391
Piedmont	temperature, bed	0.4341***	0.4318***	0.0268

¹ * P < 0.05, ** P < 0.01, *** P < 0.001.
² Partial correlation of the species matrix with stream variables, accounting for the effect of distance.
³Partial correlation of the species matrix with distance variables, accounting for the effect of stream variables.
⁴Due to the low number of sites (n = 6), simple and partial Mantel tests were not calculated for Sandhills collections during the summer.