Sorry atlanticus, you are not my type: molecular assessment splits Zophoscolex (Lumbricidae: Crassiclitellata) into French and Iberian genera

Molecular phylogenetics contributes to making important advances in the challenging field of earthworm taxonomy. Use of this type of analysis has enabled clarification of the phylogenetic relationships between early-branching genera of Lumbricidae within the highly diverse Franco-Iberian realm. However, molecular phylogenetic studies of the genus Zophoscolex are scarce and have led to taxonomic uncertainty due to insufficient sampling and the absence of the type species, Z. atlanticus, from such studies. The present study investigated 11 species of Zophoscolex (including Z. atlanticus), and the phylogenetic relationships were deduced from seven molecular markers (COI, COII, 16S, tRNAs, ND1, 12S, 28S) by Bayesian and maximum likelihood inference. The findings show that species of Zophoscolex did not belong to a single clade. Zophoscolex atlanticus was placed in a clade with Z. micellus, Z. graffi and Ethnodrilus zajonci. Other species of the genus were found to belong to the genera Cataladrilus and Compostelandrilus. Finally, most of the Iberian species form a distinct clade, which was formally described as the revised genus Castellodrilus. Based on these findings, Zophoscolex is restricted to French representatives. These results highlight the importance of incorporating type species in molecular phylogenetic analyses in order to reconcile taxonomy and systematics.

Automated summary

Molecular phylogenetics has made significant contributions to earthworm taxonomy, particularly in studying the Lumbricidae genus. This study investigated Zophoscolex species and found that they do not belong to a single clade. Z. atlanticus was closely related to several other species, while other species belong to different genera.