Detection of invasive and alien land planarians as threats to agriculture and ecosystem stability

Abstract

Alien land planarians are considered potential threats to European agriculture and ecosystem stability. Severe impact of alien land planarian species in Europe but also worldwide was reported including depletion of local and native soil invertebrates and possible detrimental changes at the ecosystem level. Given the increasing number of studies reporting non-native and potentially invasive species of geoplanid planarians, further action in first response related to worldwide plant trade is called for. To date, the only flatworm on the list of “Invasive Alien Species of European Union Concern” is the New Zealand flatworm Arthurdendyus triangulatus. To help authorities detect and prevent introduction of the New Zealand flatworm, we designed an experiment in order to develop a species-specific barcoding protocol to check possible contamination by A. triangulatus of containerised flowerpots, identified as the most probable source of its co-introduction to non-native region. Based on our results, specific behavior of A. triangulatus staying restricted to the surface and upper layer of the flowerpot determines accessibility of DNA in the soil. Therefore, water-based eDNA methodology combined with a newly established qPCR protocol is preferred as it provides a sensitive approach for detection of A. triangulatus in the flowerpots. Further testing is needed to determine sensitivity of the persistence of eDNA following the flatworm’s removal, to estimate the risk of false positives. The newly designed barcoding protocols provide species-specific diagnosis of one invasive and three non-native land planarians currently being assessed for their invasion risks. However, the species-specificity of the developed barcoding protocols might need to be re-evaluated in case of introduction of new planarian species, and in view of apparent misidentifications regarding published genetic resources. Instead, general protocols requiring genetic sequence analyses would offer a more robust approach to assess species diversity of introduced and potentially invasive land planarians.