title: Environmental DNA (eDNA) detects the invasive rusty crayfishOrconectes rusticusat low abundances.
abstract: Early detection is invaluable for the cost-effective control and eradication of invasive species, yet many traditional sampling techniques are ineffective at the low population abundances found at the onset of the invasion process. Environmental DNA (eDNA) is a promising and sensitive tool for early detection of some invasive species, but its efficacy has not yet been evaluated for many taxonomic groups and habitat types.We evaluated the ability of eDNA to detect the invasive rusty crayfishOrconectes rusticusand to reflect patterns of its relative abundance, in upper Midwest, USA, inland lakes. We paired conventional baited trapping as a measure of crayfish relative abundance with water samples for eDNA, which were analysed in the laboratory with a qPCR assay. We modelled detection probability forO. rusticuseDNA using relative abundance and site characteristics as covariates and also tested the relationship between eDNA copy number andO. rusticusrelative abundance.We detectedO. rusticuseDNA in all lakes where this species was collected by trapping, down to low relative abundances, as well as in two lakes where trap catch was zero. Detection probability ofO. rusticuseDNA was well predicted by relative abundance of this species and lake water clarity. However, there was poor correspondence between eDNA copy number andO. rusticusrelative abundance estimated by trap catches.Synthesis and applications. Our study demonstrates a field and laboratory protocol for eDNA monitoring of crayfish invasions, with results of statistical models that provide guidance of sampling effort and detection probabilities for researchers in other regions and systems. We propose eDNA be included as a tool in surveillance for invasive or imperilled crayfishes and other benthic arthropods.
authors: Department of Biological Sciences University of Notre Dame Notre Dame IN 46556 USA; Catholic Theological Union Chicago IL 60615 USA.
authors: Matthew M
authors: MM
authors: Dougherty
authors: Daniel P. Haerther Center for Conservation and Research John G. Shedd Aquarium Chicago IL 60605 USA; Environmental Change Initiative University of Notre Dame South Bend IN 46617 USA; Department of Natural Resources and Environmental Sciences University of Illinois Urbana IL 61801 USA.
authors: Eric R
authors: ER
authors: Larson
authors: Department of Biological Sciences University of Notre Dame Notre Dame IN 46556 USA.
authors: Mark A
authors: MA
authors: Renshaw
authors: Department of Biological Sciences University of Notre Dame Notre Dame IN 46556 USA.
authors: Crysta A
authors: CA
authors: Gantz
authors: Department of BioSciences Rice University Houston TX 77251 USA.
authors: Scott P
authors: SP
authors: Egan
authors: Department of Biological Sciences University of Notre Dame Notre Dame IN 46556 USA.
authors: Daniel M
authors: DM
authors: Erickson
authors: Department of Biological Sciences University of Notre Dame Notre Dame IN 46556 USA; Environmental Change Initiative University of Notre Dame South Bend IN 46617 USA.
authors: David M
authors: DM
authors: Lodge
keywords: crayfish; detection probability; early detection; early warning; exotic species; invasive species; lake; non‐indigenous; occupancy estimation; quantitative PCR (qPCR)