Temporal integration of diurnal and nocturnal interactions enhances the robustness of plant-pollinator networks

Global pollinator declines necessitate a comprehensive understanding of the mechanisms that underpin the stability of plant-pollinator networks. However, ecological network research has historically been biased toward diurnal species, neglecting how nocturnal interactions influence overall stability. To address this gap, we compiled a comprehensive dataset of 23 multilayer pollination networks, modeling diel networks as two temporal layers, diurnal and nocturnal, connected by shared plant species globally. We revealed an asymmetric structure between the two layers. The diurnal layer was more species rich and accounted for a greater proportion of core-core interactions, whereas the nocturnal layer exhibited a greater proportion of periphery pollinators and interactions. Crucially, compared with either isolated layer, the integration of these layers into a full diel network generated emergent properties, including higher relative nestedness and significantly greater robustness to pollinator extinctions (under random extinctions, mean diel plant/pollination robustness was 72.6%/47.4% [vs. 68.6%/44.9% diurnal and 62.3%/44.0% nocturnal]; when species were removed by PageRank versatility, these two values reached 88.8%/68.4% [vs. 83.4%/63.2% diurnal and 77.4%/58.7% nocturnal]; and when removed by degree versatility, they reached 87.3%/68.7% [vs. 82.5%/63.3% diurnal and 75.2%/58.9% nocturnal]). This finding was underpinned by a structure of temporal continuity, where shared diel plants acted as core hubs, demonstrating high versatility and low modular adjustability, thereby stabilizing the community across the 24-h cycle. Furthermore, robustness was primarily driven by connectance, whereas multilayer modularity surprisingly showed a significant negative effect, suggesting strong compartmentalization can limit critical compensatory dynamics across modules. Our findings established that the integration of diurnal and nocturnal interactions is a key determinant of pollination network robustness. Therefore, conservation strategies must adopt a full 24-h perspective, prioritizing the protection of core diel plants to safeguard ecosystem resilience under anthropogenic pressure.