The evolution of ecological networks Plants and the animals that eat their fruits and disperse their seeds form complex networks of mutualistic interactions. The structures of many such networks and the ecological forces that shape them are well known, but their deeper evolutionary history has received little attention. Burin et al. address this knowledge gap in a study of frugivorious bird species in documented seed-dispersal networks around the world (see the Perspective by Bello and Barreto). Species occupying central positions in frugivory networks, which thus interact with many plant species, tend to belong to lineages that are more stable over macroevolutionary time scales. These patterns are more evident in regions with warmer and wetter climates and provide evidence that evolutionary processes can leave a signal on the structure of current ecological networks. Science , this issue p. 733 see also p. 682