The article by Jordi Bascompte, Pedro Jordano, Carlos J. Melián, and Jens M. Olesen examines the structural organization of plant–animal mutualistic networks, which are typically studied with a small number of species. The authors analyze 52 mutualistic networks and find that these networks are highly nested, meaning that more specialist species interact only with proper subsets of those species that interact with more generalist species. This nestedness generates highly asymmetrical interactions and organizes the community around a central core of interactions. The study shows that nestedness increases with the complexity (number of interactions) of the network, and communities with more interactions are significantly more nested. The results suggest a nonrandom pattern of community organization that may be crucial for understanding the maintenance and persistence of biodiversity in species-rich mutualistic networks. The authors also discuss the implications of nestedness for community persistence and coevolution, highlighting the importance of a cohesive network structure and asymmetric interactions in supporting rare species and driving community evolution.The article by Jordi Bascompte, Pedro Jordano, Carlos J. Melián, and Jens M. Olesen examines the structural organization of plant–animal mutualistic networks, which are typically studied with a small number of species. The authors analyze 52 mutualistic networks and find that these networks are highly nested, meaning that more specialist species interact only with proper subsets of those species that interact with more generalist species. This nestedness generates highly asymmetrical interactions and organizes the community around a central core of interactions. The study shows that nestedness increases with the complexity (number of interactions) of the network, and communities with more interactions are significantly more nested. The results suggest a nonrandom pattern of community organization that may be crucial for understanding the maintenance and persistence of biodiversity in species-rich mutualistic networks. The authors also discuss the implications of nestedness for community persistence and coevolution, highlighting the importance of a cohesive network structure and asymmetric interactions in supporting rare species and driving community evolution.