Deciphering plant-insect interactions in a diverse urban botanical garden and the implications for developing urban planting schemes

Planting schemes in urban settings are important for increasing biodiversity and maintaining connectivity for ensuring proper ecosystem functioning. Despite this, relatively little is known regarding the ecological value of taxa planted in gardens, and more focus is on aesthetics and other sustainability  features (e.g., drought resistance). In the context of insect decline globally, and in the UK, it is important to consider the role that urban plants play in maintaining and enhancing diversity of insects. This project proposes to quantify insect diversity within a small urban botanical garden collection, using multiple methods including a novel DNA-based method using trace eDNA that insects leave behind on plants. There is potential for eDNA metabarcoding to provide insight into the wider arthropod community (e.g., pests, parasites, predators, as well as pollinators; Johnson et al., 2023). However, caution must be applied as several recent studies have shown that some known pollinator species are seemingly absent, or in lower-than-expected abundance in eDNA samples (Coster et al., 2025 Jones et al., 2025). This could be due to methodological reasons that need careful consideration (e.g., primer bias), or due to aspects of ecology (e.g., some pollinators leaving behind smaller traces of DNA in the flower environment). Thus, this suggests a multi-methods approach may give the most comprehensive and nuanced picture of plant-insect interactions. We propose to compare eDNA, camera trap observations (e.g., Droissart et al., 2021), and pollen analysis (e.g. Jones 2012).

These results will then enable us to quantify which plants produce the greatest number of interactions, and/or those that harbour unique interactions with rare or specialist insect groups. We can also quantify the type of interaction present. Ultimately the results of these analyses will then give us evidence upon which to provide suggestions for urban planting schemes, based on different criteria relating to their benefit for pollinators and other insect species.