The spread and distribution of terrestrial planarians (Turbellaria: Tricladida: Geoplanidae) within New Zealand

The New Zealand flatworm, Arthurdendyus triangulatus (formerly Artioposthia triangulata) has become established in the British Isles and the Faroe Islands and its human-mediated spread within Northern Ireland and Scotland is well documented. The geographical distributions within New Zealand of it and two related species, A. australis and A. testacea have always been assumed to reflect the natural distribution patterns. However, an analysis of the vegetation groups where the flatworms are presently found suggests that within New Zealand the distributions of endemic terrestrial planarians have been extended significantly by human intervention. Delineation of present distribution patterns of these species within New Zealand may lead to a better understanding of their potential distribution in other countries if they ever became established in them. Such extensions of ranges of New Zealand endemics within the country have implications for biodiversity analyses.