Determinants of indirect effects. (A) Scatters are indirect effects of different types of mutualistic ecosystems; grey bars and colored bars show average direct and indirect effects, respectively. (B) For the majority of all four types of networks, species’ indirect effects have no significant relation to their degrees (especially PL and SD, ), while in some networks (PA and AF) species’ indirect effects are negatively correlated with their degrees. (C) Indirect effects of multi-types of mutualistic networks increase along the gradient based on PC1 of principal component analysis, where well connected and nested networks (negative PC1 values) have small indirect effects, and modular, heterogeneous, large networks (positive PC1 values) have large indirect effects. The two networks in (C) show different structures (PL/AF) with large/small PC1 values and indirect effects, respectively. In (A)–(C), different colors represent different mutualistic networks: PL: plant-pollinator, SD: seed-dispersal, PA: plant-ant, AF: anemone-fish. Parameters: , threshold .