Rolling into the deep of the land planarian genus Choeradoplana (Tricladida, Continenticola, Geoplanidae) taxonomy

Abstract

The land planarian genus Choeradoplana (Plathelminthes, Tricladida) is currently integrated by 13 species. In previous works, morphological variation in its type species, Choeradoplana iheringi, was reported, but no attempt to test whether it is just a single species has been made yet. In order to disentangle the taxonomy of this species and further members of the genus, we sampled new specimens and combined morphological and molecular data and also have evaluated the performance of diverse methods of molecular species delimitation. Our data point to the presence of two cryptic species named C. iheringi, plus two new species, all hidden under the same general appearance. An in-depth morphological study of the specimens allowed detection of diagnostic morphological traits in each species, for which we also propose a molecular diagnosis. This integrative taxonomic study demonstrates once again the usefulness of molecular tools to weigh minor morphological characteristics and thus reveal the existence of species that would otherwise remain cryptic. However, under certain parameters, the molecular methods may over-split species with a high genetic structure, maybe pointing to incipient speciation. This makes critical the use of these methods combined with a comprehensive morphological approach. We also present a comprehensive phylogenetic tree including most Choeradoplana species. The tree, well supported, allows making some preliminary inferences on the evolution of the group and its historical biogeography.