DOI: 10.5061/dryad.0ck3q
title: Data from: Environmental DNA surveillance for invertebrate species: advantages and technical limitations to detect invasive crayfish Procambarus clarkii in freshwater ponds

description: 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.
description: 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.xlsx