McDevitt, A. | bioRxiv Science

bioRxiv2019

Fishing for mammals: landscape-level monitoring of terrestrial and semi-aquatic communities using eDNA from lotic ecosystems

O_LIEnvironmental DNA (eDNA) metabarcoding has revolutionised biomonitoring in both marine and freshwater ecosystems. However, for semi-aquatic and terrestrial animals, the application of this technique remains relatively untested.\nC_LIO_LIWe first assess the efficiency of eDNA metabarcoding in detecting semi-aquatic and terrestrial mammals in natural lotic ecosystems in the UK by comparing sequence data recovered from water and sediment samples to the mammalian communities expected from historical data. Secondly, we evaluate the detection efficiency of eDNA samples compared to multiple conventional non-invasive survey methods (latrine surveys and camera trapping) using occupancy modelling.\nC_LIO_LIeDNA metabarcoding detected a large proportion of the expected mammalian community within each area. Common species in the areas were detected at the majority of sites. Several key species of conservation concern in the UK were detected by eDNA in areas where authenticated records do not currently exist, but potential false positives were also identified for several non-native species.\nC_LIO_LIWater-based eDNA samples provided comparable results to conventional survey methods in per unit of survey effort for three species (water vole, field vole, and red deer) using occupancy models. The comparison between survey effort to reach a detection probability of [≥]0.95 revealed that 3-6 water replicates would be equivalent to 3-5 latrine surveys and 5-30 weeks of single camera deployment, depending on the species.\nC_LIO_LISynthesis and Applications. eDNA metabarcoding represents an extremely promising tool for monitoring mammals, allowing for the detection of multiple species simultaneously, and provides comparable results to widely-used conventional survey methods. eDNA from freshwater systems delivers a terrestrial dividend by detecting both semi-aquatic and terrestrial mammalian communities, and provides a basis for future monitoring at a landscape level over larger spatial and temporal scales (i.e. long-term monitoring at national levels).\nC_LI

ecology↗

bioRxiv2019

Environmental DNA (eDNA) metabarcoding of pond water as a tool to survey conservation and management priority mammals

O_LIEnvironmental DNA (eDNA) metabarcoding is largely used to survey aquatic communities, but can also provide data on terrestrial taxa utilising aquatic habitats. However, the entry, dispersal, and detection of terrestrial species DNA within waterbodies is understudied. C_LIO_LIWe evaluated eDNA metabarcoding of pond water for monitoring semi-aquatic, ground-dwelling, and arboreal mammals, and examined spatiotemporal variation in mammal eDNA signals using experiments in captive and wild conditions. C_LIO_LIWe selected nine focal species of conservation and management concern: European water vole, European otter, Eurasian beaver, European hedgehog, European badger, red deer, Eurasian lynx, red squirrel, and European pine marten. We hypothesised that eDNA signals (i.e. proportional read counts) would be stronger for semi-aquatic than terrestrial species, and at sites where mammals exhibited behaviours (e.g. swimming, urination). We tested this by sampling waterbodies in enclosures of captive focal species at specific sites where behaviours had been observed ( directed sampling) and at equidistant intervals along the shoreline ( stratified sampling). We then surveyed natural ponds (N = 6) where focal species were present using stratified water sampling, camera traps, and field signs. eDNA samples were metabarcoded using vertebrate-specific primers. C_LIO_LIAll focal species were detected in captivity. eDNA signal strength did not differ between directed and stratified samples across or within species, between species lifestyles (i.e. semi-aquatic, ground-dwelling, arboreal), or according to behaviours. Therefore, eDNA was evenly distributed within artificial waterbodies. Conversely, eDNA was unevenly distributed in natural ponds. eDNA metabarcoding, camera trapping, and field signs detected beaver, red deer, and roe deer. Badger and red fox were recorded with cameras and field signs, but not eDNA metabarcoding. However, eDNA metabarcoding detected small mammals missed by cameras and field signs, e.g. water vole. Terrestrial mammal eDNA signals were weaker and detected in fewer samples than semi-aquatic mammal eDNA signals. C_LIO_LIeDNA metabarcoding has potential for inclusion in mammal monitoring schemes by enabling large-scale, multi-species distribution assessment for priority and difficult to survey species, and could provide early indication of range expansions or contractions. However, eDNA surveys need high spatiotemporal resolution and metabarcoding biases require further investigation before this tool is routinely implemented. C_LI

molecular biology↗