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Plant–pollinator network studies have uncovered important generalities in the structure of these communities, rapidly advancing our understanding of the underlying drivers of such a structure. In spite of this, however, it is still unclear how changes in structural network properties influence overall plant pollination success. One key limitation is the lack of information on the relationship between network structural properties and aspects of pollination and plant reproductive success. Here, we estimate four plant species network structural metrics (interaction strength, weighted degree, closeness centrality, and specialization level), commonly used to describe their importance within plant–pollinator networks, at two different sites, and evaluate their effects on pollen deposition and pollen tube success. We found a positive effect of plant–pollinator specialization and a negative effect of closeness centrality on heterospecific pollen load size. We also found a marginal negative effect of closeness centrality on pollen tube success. Our results suggest that increasing plant–pollinator specialization within nested communities (pollinated by one or very few generalist insect species) may result in high levels of heterospecific pollen transfer. Furthermore, the differential effects of plant–pollinator network metrics on pollination success (pollen receipt and pollen tube success), highlight the need to integrate quantity (e.g. visitation rate) and quality (e.g. pollen delivery) aspects of pollination to achieve a more mechanistic understanding of the relationship between plant–pollinator network structure and function. Such knowledge is key to evaluate the resilience and stability of plant–pollinator communities and the services they provide in the face of increasing human disturbances.

Background: Pollen transfer via animals is necessary for reproduction by ~80 % of flowering plants, and most of these plants live in multispecies communities where they can share pollinators. While diffuse plant-pollinator interactions are increasingly recognized as the rule rather than the exception, their fitness consequences cannot be deduced from flower visitation alone, so other proxies, functionally closer to seed production and amenable for use in a broad variety of diverse communities, are necessary. Scope: We conceptually summarize how the study of pollen on stigmas of spent flowers can reflect key drivers and functional aspects of the plant-pollinator interaction (e.g. competition, facilitation or commensalism). We critically evaluate how variable visitation rates and other factors (pollinator pool and floral avoidance) can give rise to different relationships between heterospecific pollen and (1) conspecific pollen on the stigma and (2) conspecific tubes/grain in the style, revealing the complexity of potential interpretations. We advise on best practices for using these proxies, noting the assumptions and caveats involved in their use, and explicate what additional data are required to verify interpretation of given patterns. Conclusions: We conclude that characterizing pollen on stigmas of spent flowers provides an attainable indirect measure of pollination interactions, but given the complex processes of pollen transfer that generate patterns of conspecific-heterospecific pollen on stigmas these cannot alone determine whether competition or facilitation are the underlying drivers. Thus, functional tests are also needed to validate these hypotheses.