Characterizing the Microbiome of Floral Nectar of Asclepias syriaca and other Asclepias species

In recent decades, Danaus plexippus (the monarch butterfly) has experienced a drastic decrease in population size due to urbanization, climate change, and habitat loss. The primary habitat and food source of D. plexippus is plant species that are within the genus Asclepias (milkweed). The preservation and propagation of Asclepias spp. is necessary to combat D. plexippus’s population declines. A plant’s reproductive success is dependent upon its ability to attract pollinators, which is linked to the plant’s nectar qualities. We propose that, in turn, these nectar qualities may be influenced by the nectar microbiome. This study aims to better understand the plant-pollinator relationships of A. syriaca by characterizing its nectar microbiome and investigating the role of pollinators in shaping this microbial community. Bacterial community composition was assessed using 16S rRNA sequencing and epifluorescence microscopy was used to determine bacterial and viral abundance. Regardless of whether or not an umbel was exposed to pollinators, Alphaproteobacteria, Gammaproteobacteria, and Cyanobacteria/Chloroplasts were found to be the dominant taxonomic groups in A. syriaca nectar. Unlike in previous studies, pollinator interactions were not found to increase microbial diversity, but they did cause significant changes in community composition. Pollinator interactions did not cause any significant changes in bacterial or viral abundance. However, the experiment design of this study could be improved to better control pollinator-plant interactions. It is difficult to draw definite conclusions from these results, based on these design issues