Effects of Habitat Types on Pollinators and Seasonal Variations in Plant–Insect Pollination Networks in Nanchong, China

Land-use type acts as a key anthropogenic factor shaping the diversity of pollinator communities. Different habitats indirectly alter pollinator species richness, abundance and community structure by regulating vegetation coverage and the abundance of host and nectar plants. To clarify the mechanisms underlying habitat effects on pollinator assemblages, we conducted transect surveys to investigate pollinator communities across three typical habitats (forest, cropland and urban area) in Nanchong City. Our results revealed that pollinator alpha diversity was significantly higher in forests than in croplands and urban areas, with urban habitats harboring the lowest species diversity. Vegetation coverage and nectar plant richness were identified as the primary environmental drivers of pollinator diversity. The plant–pollinator interaction network exhibited pronounced seasonal dynamics: spring networks displayed a distinct nested architecture dominated by generalized mutualistic interactions; networks shifted gradually from generalized to specialized links in early summer; and only a small number of specialist pollinators persisted in late summer to early autumn. Accordingly, retaining wild flowering herbs adjacent to pollinator-dependent crops and conserving autumn- and winter-blooming plant species can sustain continuous floral food resources for pollinators, promote pollinator richness, stabilize pollinator communities, and enhance the ecosystem service of pollination.