The information insects leave behind: spatial and temporal variation of benthic assemblages using novel non-invasive methods

Abstract

Rare and elusive benthic macroinvertebrate (BMI) taxa are difficult to detect and sampling methods often require preserving live specimens, a concern for monitoring species-at-risk. Here, we aim to understand spatial and temporal variation in BMI communities within a complex, understudied river-wetland system using exuviae (shed exoskeletons), environmental DNA (eDNA) water samples and bulk-sequenced benthic samples. Samples were collected across wetland, tributary, and mainstem habitats within the lower Saint John River and Grand Lake Meadows, New Brunswick. Using exuviae, we demonstrate that terrestrial factors (e.g. riparian vegetation community) affect emergent dragonfly community composition more than aquatic factors (e.g. water temperature). Further, BMI communities identified via eDNA water samples did not differ from bulk-sequenced benthic communities, except during higher flow conditions in larger systems. Using non-invasive methods to capture biodiversity allowed us to explore ecological linkages, crossing boundaries between life stages and ecotones, to elucidate mechanisms between spatial and temporal drivers of BMI communities in a complex river-wetland system.