Pronounced temporal variability of plant-pollinator networks in response to changing precipitation in the southern Chihuahuan Desert.

Plant-pollinator interactions are essential for maintaining biodiversity and ecosystem functioning. Their analysis through ecological networks enables the assessment of the structure, resilience, and temporal dynamics of these mutualistic systems. However, research on the temporal variation of pollination networks is scarce for arid and semi-arid environments, where biological communities are highly dynamic due to climate variability. Here, we characterized the temporal variation of plant-pollinator networks in a semi-arid scrubland of the southern Chihuahuan Desert across two years with contrasting precipitation. We conducted monthly surveys of pollination interactions, reconstructed temporally discrete networks for three seasons of each year, and evaluated intra- and inter-annual changes in network composition, structure, and robustness to species loss. Interaction variability was modulated by precipitation dynamics, more pronounced among seasons of the same year than between years, and mainly driven by temporal turnover of the plant species in bloom. Greater rainfall was linked to higher plant and pollinator richness and a greater number of connectors, module hubs, and network hubs, especially herbs, dipterans, and lepidopterans. We recorded substantial temporal variation in species' structural roles, yet highlight the importance of generalist bees for network cohesion over time. Seasonal networks showed a persistent compound topology, where nestedness occurs within modules rather than at the whole-network scale. Specialization and modularity tended to increase under drought conditions, accompanied by a decrease in network robustness to species loss. Our results underscore the remarkable diversity and plasticity of plant-pollinator networks in semi-arid environments and provide valuable insights for their conservation under climate change scenarios.