Diurnal versus nocturnal pollination in a subalpine wetland: From network structure to plant reproduction

Abstract

Diurnal and nocturnal pollinators are fundamental for the functioning of natural ecosystems and food security. However, differences between diurnal and nocturnal pollination networks and the contribution of these pollinators to plant fecundity have not been assessed comprehensively within a community context. In the Dajiuhu subalpine wetland of central China, we supplemented data from an intensive field survey with the analysis of pollen loads carried by diurnal and nocturnal pollinators to compare the structures of diurnal and nocturnal pollination networks using network parameters. Simultaneously, we compared the contribution of diurnal and nocturnal pollinators to plant reproduction of the nine dominant species based on stigma pollen placement. We found that although diurnal and nocturnal pollination networks exhibited a similar structural organisation, the diurnal network displayed greater stability and broader interaction with pollinators and plants compared to the nocturnal network. However, nocturnal pollinator species tended to establish less generalised interactions with the available floral resources. Both diurnal and nocturnal pollinators played a significant role in plant reproduction, and nocturnal pollination can result in greater pollen germination. In terms of stability, the lower redundancy of links within nocturnal networks suggests they may be more vulnerable to the temporary or permanent disappearance of plant resources in the study area. Our findings highlight the differences in the contributions of diurnal and nocturnal pollinators to plant reproduction at the community level, demonstrating that nocturnal pollinators are not redundant in maintaining species diversity in communities. This knowledge should play a pivotal role in preventing future pollination declines and improving pollinator conservation efforts.