Structure And Dynamics Of Pollination Networks In Wuhan University

Urban ecosystems have become emerging pollination hotspots due to their rich floral resources and highly heterogeneous habitats.However,to date,pollination studies in urban ecosystems have mostly focused on plant and pollinator diversity,while the structure and dynamics of pollination networks have not been reported.In this study,we selected Wuhan University,an urban ecosystem,and integrated its two pollination networks: plant-pollinator interaction network and heterospecific pollen transfer network,to conduct the following studies.Firstly,we investigated the composition of plants and pollinators in Wuhan University at a monthly frequency and established plant-pollinator interaction networks to investigate their structure properties and temporal dynamic patterns.We found that both plant and pollinator species and the number of their interactions varied from month to month.The comparison of the parameters of the monthly-level plant-pollinator interaction networks with those of the yearly cumulative interaction network revealed that the monthly interaction networks had higher flexibility than the yearly cumulative network.The species-level parameters of plants that recurred for at least 3 months were not the same in each month,suggesting that the same species has different network status in different interaction networks.We explored the reasons for the above dynamics in the interaction network and found that the main drivers were species turnover and interaction rewiring.Species turnover played a greater role in the dynamics of the interaction networks in 2019,while in 2020 it was mainly driven by interaction rewiring.Secondly,we measured the pollen deposition on terminal stigmas of each plant species surveyed each month,recorded the number and germination of conspecific and heterospecific pollen deposited on the terminal stigmas,then we established heterospecific pollen transfer networks based on the interspecific pollen exchange.We found that interspecific pollen exchange was prevalent in every month.Analyzing the network-level parameters and species-level parameters(including only plants that recurred for at least 3 months)of the heterospecific pollen transfer networks for each month,we found that both the overall network structure and the contribution of the same species to different networks differed significantly from month to month.In addition,we analyzed the correlation between monthly pollinator species richness,the number of plant-pollinator interactions and different parameters of the heterospecific pollen transfer networks,respectively.And we found that the more complex the heterospecific pollen transfer networks,the higher pollinator species richness there were,while it did not correlate with the number of interactions.Lastly,we classified all the plants surveyed in each month into two types,cultivated and wild,and compared their position in the pollination networks.In the plant-pollinator interaction networks,wild plants were significantly more specialized in the annual cumulative network than cultivated plants,indicating that wild plants have less overlapping pollination niches.In the heterospecific pollen transfer networks,wild plants have higher eigenvector centrality,indicating that they have pollen exchange with more species in the networks.In summary,we revealed the composition,structure and temporal dynamics of urban pollination networks in a more comprehensive manner,which can provide a methodological reference for future comprehensive studies on pollination networks in urban ecosystems.Furthermore,our study of the variations in the structure of dynamic pollination networks and the changes in the network roles of various species suggest that the diversity of species interactions can be explored to a greater extent when focusing on the temporal dynamics of the network,which is more useful for understanding the generation and maintenance of community biodiversity and thus ensuring the harmonious and balanced development of ecosystems.