Running to the mountains: changes in plant-pollinator networks structure over space.

Plant-pollinator networks play a crucial role in supporting biodiversity and ecosystem functioning, especially in mountainous regions. Plant-pollinators networks experience various influences from biotic and abiotic factors across elevation gradients and flowering seasons, impacting species distribution, interactions, and community structures. In our study, we examined plant-pollinator network structures at 14 sites across elevations from 1000 to 1800 m above sea level in a Mediterranean mountainous area. The study aimed to determine if plant-pollinator network structures remain consistent across different spatial contexts (elevations and habitats) and to assess the impact of abiotic drivers on network structure. We documented a total of 3343 interactions involving 343 pollinator species and 44 plant species, with bees and flies as prominent participants. Results showed low nestedness, which increased only with rainfall, and was generally higher in forests than in outcrop areas. High specialization was noted, with an increase in specialization correlated with rainfall. Network modularity was more pronounced in outcrops compared to forests, with soil temperature and rainfall boosting modularity. Interaction diversity was greater in outcrops and showed a positive relationship with rainfall. High robustness correlated inversely with specialization. Our findings highlight that flower and pollinator diversity, combined with climatic factors, predict network modularity, specialization, and robustness. This research illustrates how network structures differ across habitat types and elevation, revealing potential vulnerabilities of plant-pollinator interactions to environmental changes throughout the flowering season. We also highlight the potential impact of climate change on pollination networks on mountain areas (as hotspots of biodiversity).