The mutualistic interactions between plants and the animals that pollinate them or disperse their seeds can form complex networks involving dozens or hundreds of species. These networks show general architectural patterns that may maximize the number of coexisting species and increase the range of variability that these mutualistic networks can withstand. However, because phylogenetically similar species tend to play similar roles in the network, extinction events may trigger non-random coextinction cascades, thus leading to a faster loss of taxonomic diversity. From an evolutionary point of view, the indirect effects arising from these network patterns may drive trait coevolution within species-rich assemblages.