Partitioning wild bee and hoverfly contributions to plant–pollinator network structure in fragmented habitats

Abstract

The risk of ecosystem function degradation with biodiversity loss has emerged as a major scientific concern in recent years. Possible relationships between taxonomic diversity and magnitude and stability of ecosystem processes build upon species' functional characteristics, which determine both susceptibility to environmental change and contribution to ecosystem properties. The functional diversity within communities thus provides a potential buffer against environmental disturbance, especially for properties emerging from interactions among species. In complex plant–pollinator networks, distantly related taxa spanning a great trait diversity shape network architecture. Here, we address the question of whether network properties are maintained after habitat loss by complementary contributions of phylogenetically distant pollinator taxa. We quantified contributions of wild bees and hoverflies to network structure (connectance, network specialization, specialization asymmetry) in 32 calcareous grassland fragments varying in size. Although hoverflies are often regarded less susceptible to environmental change than wild bees, species richness of both taxa was similarly affected by habitat loss. The associated loss of 80% of interactions resulted in small and tightly connected networks, which was more strongly attributed to wild bee loss than hoverfly loss. Networks in small fragments were less specialized due to equivalent losses of species and interactions in both pollinators and plants. Because wild bee and hoverfly loss contributed similarly to declining network specialization, we conclude that trait diversity among distantly related pollinators does not necessarily provide insurance against functional homogenization during community disassembly following habitat loss.

Forest fragmentation modifies the composition of bumblebee communities and modulates their trophic and competitive interactions for pollination

“…Likely, the positive relationship between flower density and network specialization is due to resource partitioning 19,70,71 , as increases in flower availability might increase the possibilities of bumblebee species to focus on different resources to optimize foraging and avoid competition 15 . Our results regarding patch shape complexity are in the line of other studies that also found a negative relationship between network specialization and habitat loss or disturbance 23,26 . The reasons for a decrease in network specialization as patch shape complexity increases might be twofold.…”

Quantifying habitat and landscape effects on composition and structure of plant-pollinator networks in the US Northern Great Plains

“…Approximately 50% of the interactions in our plant-pollinator networks were dominated by syrphid flies and apid bees, which are highly mobile and utilize a variety of habitat types, indicating the insect pollinators in our observed networks may have traveled considerable distances to utilize the semi-natural reservoirs embedded within this cropland matrix. (Morris 1993;Sommaggio et al 1999;Beekman and Ratneiks 2000;Klecka et al 2018;Jauker et al 2019). These findings are also consistent with other studies such as Winfree et al (2007) and Hoehn et al (2008) demonstrating that landscapes dominated by intensive agriculture can still maintain relatively diverse pollinator communities provided patches of floral resources were present.…”

“…Nevertheless, there is an alarming global decline of insect pollinators largely attributed to anthropogenic pressures such as land-use intensification and widespread use of pesticides (Kearns et al 1998;Steffan-Dewenter et al 2005). Given these documented declines, there is an increased interest in conserving pollinator communities and their habitats to stabilize these critical ecosystem services and in turn, ecosystem function (Steffan-Dewenter et al 2002;Kremen et al 2002;Olesen et al 2007;Peterson et al 2010;Redhead et al 2018;Jauker et al 2019).…”

Reconstructing Great Basin Butterfly-Pollen Interaction Networks over the Past Century

“…Numerous metrics at both the network and species level have been developed and can provide useful quantitative summaries of pollination network properties (Gibson et al, 2011;Jauker, et al, 2018). Proper interpretations of selected network parameters can help us to understand pollinators' responses to habitat alteration, biodiversity change, and climate change by comparing changes in interactions over time or across disturbance gradients (Proulx et al, 2005;Ballantyne et al, 2015;Bohan & Dumbrell, 2017).…”