Genetic diversity of<i>Ligula intestinalis</i>(Cestoda: Diphyllobothriidea) based on analysis of inter-simple sequence repeat markers

Abstract

In order to investigate the genetic diversity of Ligula intestinalis populations, nine inter-simple sequence repeat (ISSR) markers were applied to populations from nine geographical areas around the world and 10 host species. The 110 loci selected from the ISSR patterns produced revealed high variability among the analysed samples, with a polymorphism of 100% and a global coefficient of gene differentiation estimated by Nei’s index (GST) of 0.776. Major genetic differentiation was found to be correlated to five broad geographical regions (Europe, China, Canada, Australia and Algeria). Nevertheless, no significant genetic variation was found among European isolates, although they originated from disparate geographical localities and/or unrelated hosts. Classical classification methods: maximum parsimony and factorial correspondence analysis were compared with an advanced statistical method: the self-organizing map (SOM). The results demonstrated that the ISSR approach is rapid and inexpensive and provides reliable markers to assess genetic diversity of L. intestinalis. Furthermore, SOM artificial neuronal networks are considered to provide an efficient alternative tool for mapping the genetic structures of parasite populations. Resume Dans cette etude, nous avons analyse la variabilite genetique de differentes populations de Ligula intestinalis. Pour cela, 9 marqueurs des repetitions intermicrosatellites (ISSR) ont ete selectionnes et appliques a des echantillons collectes dans 9 regions geographiques du monde et dans 10 especes hotes. Les patrons ISSR ont genere 110 loci et montrent une forte variabilite avec un polymorphisme de 100% et un coefficient global de differenciation de gene estime par l’indice de Nei (GST) de 0.776. Nous trouvons une forte differentiation genetique entre 5 groupes qui correspondent a 5 larges regions geographiques (Europe, Chine, Canada, Australie et Algerie). Neanmoins aucune variation genetique significative n’a ete retrouvee parmi les echantillons Europeens, bien qu’ils soient originaires de differentes localites geographiques et/ou de differents hotes. Les methodes de classification classique : Maximum de parcimonie (MP) et l’Analyse Factorielle de Correspondance (AFC) ont ete comparees avec une methode statistique recente : les cartes auto-organisatrices (SOM). Les resultats montrent que l’approche ISSR que nous avons utilisee fournit des marqueurs fiables capables de discriminer entre differentes populations de Ligula. Les SOM representent un outil alternatif efficace pour etablir la structure genetique des populations de parasites.