Data from: Environmental DNA surveillance for invertebrate species: advantages and technical limitations to detect invasive crayfish Procambarus clarkii in freshwater ponds

1. The introduction of non-native species is a major threat to biodiversity. While eradication programs of well-established invaders are costly and hazardous for non-target species, the early detection of a non-native species at low density is critical for preventing biological invasions in recipient ecosystems. Recent studies reveal that environmental DNA (eDNA) is a powerful tool for detecting target species in aquatic ecosystems, but these studies focus mostly on fish and amphibians. 2. We examine the reliability of using eDNA to detect the presence of an invasive freshwater crustacean species, the red swamp crayfish Procambarus clarkii. Species-specific primers and probes were designed; their specificity was tested using in silico PCR simulations and against tissues of other crayfish species. Limits of detection and quantification were specified for the target DNA sequence by means of quantitative PCR amplifications on dilution series of known amount of P. clarkii DNA. 3. The method was applied to water samples collected in 158 ponds in a French Nature Park, and results were compared to a traditional method using food-baited traps. eDNA has a better detection efficiency but predominantly leads to divergent results compared with the trapping method. While habitat features partly explain the failure of crayfish detection by trapping, detection by eDNA is problematic at low crayfish abundances. When P. clarkii is detected, the estimated concentrations of crayfish DNA in water samples are always below the limit of quantification for the target DNA sequence. 4. Synthesis and applications. The combination of eDNA and conventional trapping methods is recommended to monitor the invasion by the red swamp crayfish P. clarkii in small waterbodies such as ponds. However, the risk of mortality for non-targeted species, notably amphibians, has to be carefully evaluated before the deployment of traps at large scale. Contrary to fish and amphibians, low amount of extracellular DNA in water is suspected to be the major limitation for crayfish detection by molecular approaches. Current advancements in PCR technology, together with optimization of the water sampling method, promise upcoming developments of eDNA detection for aquatic invertebrate species.Detection of Procambarus clarkii by funnel traps and environmental DNA depends on pond characteristics and crayfish abundancesThe presence of Procambarus clarkii was surveyed in a network of 158 ponds in France by using funnel traps and eDNA analyses concomitantly. Ponds were described using 6 habitat variables: perimeter, surface, maximum depth (sometimes estimated), estimated volume, mean shoreline slope and occurrence of litter. Additionally, 5 water quality variables (temperature, turbidity, conductivity, pH and dissolved oxygen) were measured on a subsample of 82 ponds. For the 51 ponds where crayfish were trapped, CPUE (catch per unit effort - number of crayfish per trap per 24h) and the proportion of juveniles were calculated.Data.xls