Guess who? Taxonomic problems in the genus Eiseniella revisited by integrated approach

Abstract

Eiseniella neapolitana is a semi-aquatic, diploid earthworm that for many years was related to the cosmopolitan species Eiseniella tetraedra and even considered a subspecies of it. Norealidys andaluciana was described in Spain and is usually synonymized with E. neapolitana. We collected 69 specimens from Italy, Spain, and Cyprus and studied five molecular markers (COI, 16S, 28S, 12S, and ND1) and their morphology to solve this taxonomic problem. Phylogenetic analyses reveal the possible existence of two separate genera confounded under the name Eiseniella, but the study of more molecular markers and species of the genus would be necessary to confirm this. Therefore, the synonymy between Eiseniella and Norealidys is maintained. Various genetic analyses, including species delimitation, confirm the separation between E. neapolitana and E. andaluciana (= N. andaluciana) and excluded that E. neapolitana is a subspecies of E. tetraedra. The resemblance in external appearance despite clear genetic differences of the three species could be explained by convergent adaptation to the aquatic habitat. Despite the expected low haplotype diversity based on the 28S gene, we found a surprisingly high variability in the E. andaluciana (= N. andaluciana) population in Spain. However, its stable predicted secondary structure and its high content of G + C reject the presence of a pseudogene.