Bee conservation faces numerous stressors including habitat loss, reduced resource availability, and increasing prevalence of generalist parasites and pathogens. Bee foraging ecology is known to link these factors together, as it has been shown that resource overlap at floral heads leads to disease transmission among bee species in the community. Infected bees have been shown experimentally to disperse infective parasite spores to multiple flowers while foraging, which can be vectored among pollinators or transmitted to other bees.
Given the predominance of foraging behavior on the ecology of infectious disease in this system, plant-pollinator-parasite networks offer an exciting method of quantifying resource overlap, disease transmission, and parasite host range. Plant-pollinator networks were observed at two sites in central Texas at two timepoints in the summer of 2018. 978 independent plant-pollinator interactions were recorded and used to build resource-overlap networks. 656 bees were collected while foraging and subsequently screened for three groups of gut parasites: Trypanosomes (ie. Crithidia bombi), Microsporidians (ie. Nosema ceranae), and Neogregarines (ie. Apicystis bombi).
Results/Conclusions
The plant-pollinator networks revealed a high degree of resource overlap among foraging bees. The most abundant bee species have the highest degree centrality, in this case a measure of diet breadth, and were also the most likely to harbor detectable parasites. The broad foraging behavior of these species may have led to broad host ranges for the parasites under investigation. In one of the networks, parasites were detected in 7 of the 18 observed bee species (39%). Furthermore, those 7 potential host species visited 81.25% of the flower species in the network. These early results indicate that generalist foraging behavior among bees and generalist host ranges in their parasites can lead to broad dispersal and transmission dynamics in natural plant-pollinator networks. In addition, this work identifies several bee species not previously reported as susceptible to these parasites.