Exploring the molecular diversity of terrestrial nemerteans (Hoplonemertea, Monostilifera, Acteonemertidae) in a continental landmass

We report the finding of terrestrial nemerteans of the family Acteonemertidae from the northern part of Spain. The specimens were studied using molecular data from the nuclear ribosomal 18S rRNA and the mitochondrial cytochrome c oxidase subunit I genes. The 18S rRNA data strongly suggest the presence of three species of terrestrial nemerteans in the Iberian Peninsula, an old landmass where terrestrial nemerteans had not previously been reported. These specimens originate from primarily undisturbed forests across a distance of c . 1000 km. Cytochrome c oxidase subunit I data also indicate the presence of multiple lineages of Iberian terrestrial nemerteans. Nonetheless, the pattern obtained from this marker is obscured most probably by deep genetic divergences. This molecular diversity, at least in some of the clades, suggests that the Iberian species are not the result of recent introductions, as proposed for other terrestrial nemerteans found in Europe. Our data also touch upon the question of a single origin of terrestriality in nemerteans, a hypothesis rejected by both data sets. Nevertheless, terrestriality seems to have had a single origin in the family Acteonemertidae.