Genetic variation in populations of the terrestrial planarian Artioposthia triangulata (Dendy), and evidence for passive dispersal in Northern Ireland

Genetic variation in 12 populations of the terrestrial planarian Artioposthia triangulata from Northern Ireland and one in the Republic of Ireland were assessed using starch-gel electrophoresis. Seven enzymes - adenylate kinase, aspartate aminotransferase, enolase, malate dehydrogenase, phosphoglucose isomerase, phosphomannose isomerase and superoxide dismutase - provided consistent, resolved stains. Coefficients of genetic identity were similar for all comparisons suggesting that the populations did not belong to distinct taxa. There was no relationship between genetic distance and geographic distance for populations, thus confirming the role of passive dispersal in the spread of A. triangulata. Average percentage polymorphic loci and mean heterozygosities were higher in the east of the Province (41.4% and 0.240), than the west (37.5% and 0.185) suggesting that the planarian had spread westwards after an initial colonisation in the east.