Ecosystems are composed of complex networks of many species interacting in different ways. While ecologists have long studied food webs of feeding interactions, recent studies increasingly focus on mutualistic networks including plants that exchange food for reproductive services provided by animals such as pollinators. Here, we synthesize both types of consumer-resource interactions to better understand the controversial effects of mutualism on ecosystems at the species, guild, and whole-community levels. We find that consumerresource mechanisms underlying plant-pollinator mutualisms can increase persistence, productivity, abundance, and temporal stability of both mutualists and non-mutualists in food webs. These effects strongly increase with floral reward productivity and are qualitatively robust to variation in the prevalence of mutualism and pollinators feeding upon resources in addition to rewards. This work advances the ability of mechanistic network theory to synthesize different types of interactions and illustrates how mutualism can enhance the diversity, stability, and function of complex ecosystems.

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Mutualisms are ubiquitous in nature and serve indispensable roles in supporting biodiversity and ecosystem function. Nearly all species on Earth participate in at least one of four main types of mutualism: seed dispersal, pollination, protection, and resource exchange including with symbionts (Bronstein, 2015a(Bronstein, , 2015bJanzen, 1985).Moreover, up to ~3/4 of phosphorus and nitrogen acquired by plants is provided by mycorrhizal fungi and nitrogen-fixing bacteria (van der Heijden et al., 2008) and ~1/3 of crop production is dependent on animal pollination (Klein et al., 2007). The last 40 years has seen an important increase in studies on population ecology of mutualism but with no (e.g., Gotelli, 2008) to some representation in ecology

Ecological networks can represent the structure of food webs, energy flow, and the many and diverse types of interactions between species in ecosystems. Despite its tremendous importance for understanding biodiversity, stability, ecosystem functioning, research on ecological networks has traditionally been restricted to subsets of the species or interactions in ecosystems, i.e., ''subnetworks'' such as pollination networks or food webs. As a result, the structure of ''multiplex'' networks that include multiple interaction types is mostly unknown and there is no robust, underlying theory to support their study. Some ecological traits, such as body size or length of mouth parts, are well-known as key predictors of different species interactions. These traits are often strongly related to each other due to evolutionary history, allometry, and selection, and this relatedness may constrain the structure of ecological multiplex networks. We use this idea to develop a model that simulates multiplex ecological networks by interconnecting subnetworks using correlated traits. Our model predicts how multiplex network structure, measured as the overlaps between species' functional roles, is affected by neutral processes, interaction rules, and trait constraints, while the structure of individual subnetworks is independent of these trait correlations. Additionally, our model accurately predicts the structure of an observed multiplex network using existing knowledge on species trait correlations and basic features of known ecological subnetworks. This work will stimulate new studies of the structure and dynamics of complex ecosystems by providing a null expectation for how multiplex ecological networks are structured under different ecological conditions.

Ecosystems are composed of complex networks of many species interacting in different ways. While ecologists have long studied food webs of feeding interactions, recent studies increasingly focus on mutualistic networks including plants that exchange food for reproductive services provided by animals such as pollinators. Here, we synthesize both types of consumer-resource interactions to better understand the controversial effects of mutualism on ecosystems at the species, guild, and whole-community levels. We find that consumer-resource mechanisms underlying plant-pollinator mutualisms can increase the persistence, productivity, abundance, and temporal stability of both mutualists and non-mutualists in food webs. These effects strongly increase with floral reward productivity and are qualitatively robust to variation in the prevalence of mutualism and pollinators feeding upon resources in addition to rewards. This work advances the ability of mechanistic network theory to synthesize different types of interactions and illustrates how mutualism can enhance the diversity, stability, and function of complex ecosystems.