Table 3.

A priori predictions, description of the results based on the analyses, and their interpretation. PaAq = actively dispersing species with aquatic adults, PaTe = passively dispersing species with terrestrial adults, AcTe = actively dispersing species with terrestrial adults, K = Koutajoki basin, I = Iijoki basin, and T = Tenojoki basin

Prediction	Result	Interpretation
(1) Pure environmental component is higher for active dispersers.
Within basins	PARTIAL SUPPORT (fraction highest except in Koutajoki when using overland distances)	Suggests that, at small spatial extents, the actively dispersing species are more able to track environmental heterogeneity than passively dispersing species.
Across basins	SUPPORTED	Suggests that, at the large spatial extent, actively dispersing species are more able to track environmental heterogeneity than passively dispersing species.
(2) Pure spatial component is higher for species with aquatic adults.
Within basins	NOT SUPPORTED	In this system, in general, the importance of spatial structuring is so low that it hinders meaningful comparisons between dispersal mode groups.
Across basins	NOT SUPPORTED	See above.
(3a) Strength of pure environmental control: AcTe > PaTe > PaAq
Within basins	PARTIAL SUPPORT (In Koutajoki with overland distances, PaTe had the highest fraction)	See prediction 1.
Across basins	NOT SUPPORTED	Due to high covariation, the effects of spatial location and environmental factors cannot be distinguished at large spatial extent.
(3b) Strength of pure spatial control: PaAq > PaTe > AcTe
Within basins	NOT SUPPORTED	See prediction 2.
Across basins	NOT SUPPORTED	See prediction 2.
(4) Spatial [b + c] fraction should be higher when using watercourse distances compared with overland distances.	NOT SUPPORTED	The two distance measures are equally good or poor in the studied system.
(5a) Environmental structuring should be highest in the drainage basin with the highest environmental heterogeneity (K > I > T)	NOT SUPPORTED	Some factor(s) other than the degree of environmental heterogeneity drove the differences among basins.
(5b) Spatial structuring should be highest in the study area with the largest spatial extent (T > I > K)	NOT SUPPORTED	Some factor(s) other than the spatial extent drove the differences among basins.