Experimental design
We studied how relative ecosystem size mediates the effect of resource flows between autotrophic and heterotrophic patches in experimental meta-ecosystems using aquatic protist microcosms (Altermatt et al., 2015). We compared meta-ecosystems containing two patches: one autotrophic and one heterotrophic patch. The total size of each of these three meta-ecosystem types was the same (i.e., the total volume of both patches per meta-ecosystem totalled always 45 mL), but they had different relative patch sizes per meta-ecosystem. The first meta-ecosystem type had a large heterotrophic and a small autotrophic patch, referred to as heterotrophic-dominated. The second meta-ecosystem type had a large autotrophic and a small heterotrophic patch, referred to as autotrophic-dominated. The third meta-ecosystem type had two medium-sized patches, referred to as equally-dominated. The volumes of the small, medium, and large patches were 7.5, 22.5, and 37.5 mL, respectively. The three meta-ecosystem types were either connected by non-living resource flows or unconnected (see Fig. 1). Equally-dominated, heterotrophic-dominated, and autotrophic-dominated connected meta-ecosystems are referred to asMAMH–MHMA ,SALH–LHSA , andLASH–SHLA , respectively (dashes indicating the two connected patches). S , M , and L refer to Small (7.5 ml), Medium (22.5 ml), and Large (37.5 ml) patches, respectively. A and H refer to autotrophic and heterotrophic patches, respectively. When looking at individual patches, subscripts refer to the size and trophic type of the connected patch (e.g., MAMH indicating that it is a medium-sized autotrophic patch connected to a medium-sized heterotrophic patch). Respective unconnected controls of the resource flow effect areMA|MH , SA|LH , and LA|SH (without subscripts; vertical line indicating that they were unconnected). All meta-ecosystems started with identical initial communities and were replicated five-fold.