Molecular analysis of the diversity of terrestrial planarians (Platyhelminthes, Tricladida, Continenticola) in the Iberian Peninsula

Abstract

This work is a prospective study to estimate the potential species diversity of terrestrial planarians in the Iberian Peninsula. Live specimens were collected from several Iberian localities and assigned to different morphotypes on the basis of their external morphological characteristics. From the same specimens, sequences from the mitochondrial Cytochrome Oxidasa subunit I (COI) and from the nuclear ribosomal gene 18S rRNA were obtained. Sequences from GenBank of the families Dendrocoelidae, Planariidae, Bipaliidae, Geoplanidae and Rhynchodemidae have been used as outgroups in the phylogenetic analysis. The results showed that terrestrial planarians have a wide distribution in the Peninsula, with all individuals found belonging to the Rhynchodemidae family. Morphological observations indicated the presence of 10 morphospecies confirmed by the molecular analyses. At the same time, COI sequences were successfully used as a molecular marker for species identification in the barcoding mode, which is of great use in groups like this with few external morphological characteristics. The combined data strongly suggest the presence of at least 15 species in the Iberian Peninsula, a number that nearly doubles previous estimates, indicating that terrestrial planarians are more diverse than expected in the region and, as proposed, may be a good biodiversity indicator and model for biogeographical studies.