Non-native land planarians (Platyhelminthes, Tricladida, Geoplanidae) in Belgium: A review and risk assessment

Abstract

Multiple species of land planarians have become established outside their natural ranges. Some are considered invasive because of their rapid spread and adverse effects on ecosystems. Once established, land planarians are difficult to manage. Therefore, it is crucial to document their presence and spread and assess their risk. This study provides an annotated checklist and distribution maps of all non-native land planarians recorded in Belgium, as well as a climate-matching analysis and a Harmonia + risk assessment for each species. A climate-matching analysis and a risk assessment were also conducted for two species that do not occur in Belgium but are included in the European Union's list of invasive alien species of Union Concern: Platydemus manokwari and Arthurdendyus triangulatus. Thus far, nine non-native land planarian species have been recorded in Belgium: Anisorhynchodemus cf. signata, Bipalium kewense, Caenoplana coerulea, C. variegata, Diversibipalium multilineatum, Dolichoplana striata, Marionfyfea adventor, Obama nungara, and Parakontikia ventrolineata. Climate-matching percentages were highest for A. triangulatus, M. adventor, C. variegata, and O. nungara. Obama nungara is the only species that received a very high environmental risk score. Diversibipalium multilineatum and P. manokwari both received high environmental risk scores. The overall risk score was medium for O. nungara and D. multilineatum and low for all other species. The information presented in this review may provide a basis for developing suitable detection and monitoring methods and rapid-response strategies for high-risk non-native land planarians.