Figure 3. A) The mean number of neighbouring ponds (+/- SE) around each pond within an increasing radius (cut-off distance), where grey shading shows the full range between minimum and maximum values. B-D) Variograms with the amount of unique variance of taxonomic richness explained by the number of ponds within a radius against each cut-off distance, grouped according to dispersal traits.
With increasing radius size around the focal pond, the number of ponds within the radius increased rapidly until around 550 meters where the curve saturates, indicating the most dense part of the pond cluster (Fig. 3 A). Accordingly, the number of ponds above this distance did not explain a considerable amount of variance in taxonomic richness in any of the studied groups (Fig. 3 B-D). At the same time, there was considerable variance in pond numbers within the scales of 150-550 m (Fig. 3 A), with related spatial signals in the local taxonomic richness of four groups (prokaryotes, rotifer and crustacean zooplankton, dipterans Fig. 3 B-D). In both zooplankton groups, the relationship between pond number and taxonomic richness was strongest within a circle radius between 200 and 400 metres, while it was 300-700 metres for dipterans. As the variation explained by the environment did not show a similar spatial structuring, this suggests that indeed neighbouring pond densities are the major driver of the observed pattern (Fig. S4).

Metacommunity structure

In metacommunity structure, the overall pattern was similar to taxonomic richness with the environment explaining more variance than space in most organism groups (Fig. 4). The amount of unique variance explained by the environment varied between 10.1 and 36.4% and it was statistically significant in all organism groups. The unique effect of space varied between 0.7 and 15.6%, being the highest in rotifers and lowest in prokaryotes (Table S5 and S6, Supporting information). It was statistically significant for prokaryotes (F(3,43)=1.14, p=0.0475), heterotrophic microeukaryotes (F(5,40)=1.21, p=0.026), rotifers (F(7,41)=1.95, p<0.001), crustaceans (F(5,44)=1.70, p=0.004), and dipterans (F(2,45)=1.96, p=0.004).