Search

In the face of global biodiversity declines, surveys of beneficial and antagonistic arthropod diversity as well as the ecological services that they provide are increasingly important in both natural and agro‐ecosystems. Conventional survey methods used to monitor these communities often require extensive taxonomic expertise and are time‐intensive, potentially limiting their application in industries such as agriculture, where arthropods often play a critical role in productivity (e.g. pollinators, pests and predators). Environmental DNA (eDNA) metabarcoding of a novel substrate, crop flowers, may offer an accurate and high throughput alternative to aid in the detection of these managed and unmanaged taxa. Here, we compared the arthropod communities detected with eDNA metabarcoding of flowers, from an agricultural species (Persea americana—'Hass' avocado), with two conventional survey techniques: digital video recording (DVR) devices and pan traps. In total, 80 eDNA flower samples, 96 h of DVRs and 48 pan trap samples were collected. Across the three methods, 49 arthropod families were identified, of which 12 were unique to the eDNA dataset. Environmental DNA metabarcoding from flowers revealed potential arthropod pollinators, as well as plant pests and parasites. Alpha diversity levels did not differ across the three survey methods although taxonomic composition varied significantly, with only 12% of arthropod families found to be common across all three methods. eDNA metabarcoding of flowers has the potential to revolutionize the way arthropod communities are monitored in natural and agro‐ecosystems, potentially detecting the response of pollinators and pests to climate change, diseases, habitat loss and other disturbances. [ABSTRACT FROM AUTHOR]

[Display omitted] • eDNA from tree crop flowers reveals variation in pollinators, pests and predators. • This molecular method detected more unique taxa than digital video recordings. • Greater detections of Hymenoptera species in the upper canopies of trees. • Arthropod communities between orchards became more similar during peak flowering. • Arthropod length did not correlate with eDNA detectability. Collating data about natural capital and the ecosystem services that underpin agricultural productivity, such as the activity of beneficial (e.g., pollinators) and antagonistic (e.g., plant pests) native and introduced arthropod taxa, is critical for timely management strategies. To date, these monitoring efforts have largely relied upon conventional survey and monitoring methods (e.g., sweep netting and morphological identifications), which are difficult to implement at the large scale of agriculture. Environmental DNA (eDNA) metabarcoding is a molecular method that amplifies trace amounts of DNA deposited by organisms from diverse substrates including soil, plant tissue and even air. In this study, we used eDNA metabarcoding of tree flowers, complemented with digital video recording (DVR) devices, to detect temporal, fine- and large-scale arthropod community changes across two Persea americana ('Hass' avocado) orchards. In total, we detected 42 arthropod families with eDNA metabarcoding. This molecular method detected five times the number of unique taxa (N = 50) compared to the DVRs (N = 10), nearly all of which are unmanaged native species. The number of arthropod eDNA detections increased by 14 % during peak flowering and included species from different functional groups including known arthropod pollinators, pests, parasites and predators. At fine-spatial scales, inflorescence samples collected in the upper and lower canopy show that Hymenoptera taxa were 13 % more likely to be detected in the upper canopy. While at large-spatial scales, eDNA metabarcoding showed that the arthropod communities in both orchards shared less than 50 % similarity at low flowering and became more similar towards peak flowering. With occupancy modelling, we determined that arthropod length did not correlate with eDNA detection probability. Our findings highlight the value of eDNA-based monitoring and illustrate that agroecosystem management requires a growing awareness that the production boundary has expanded, and that the goods and services that unmanaged arthropod species provide need to be included on the balance sheet. [ABSTRACT FROM AUTHOR]