Molecular data confirms the existence of distinct lineages within Lumbricus friendi (Cognetti 1904) and related friends

Lumbricus friendi is a lumbricid earthworm mainly found in western Europe, considerably less well studied than its close relative L. terrestris and until now, has not been a subject of taxonomical debate. However, its disjointed geographical distribution suggesting striking similarities to the Celtic fringes and of the so-called Lusitanian species merits further investigation. Our aim was to examine the genetic variation of this species and other related taxa within the genus (L. terrestris, L. rubellus, L. rubellus friendoides and L. friendi bouchei) to test for the existence of cryptic lineages that might explain its current distribution. Using mitochondrial (16S and COI) and nuclear (Amplified Fragment Length Polymorphism, AFLP) markers, we provide the first genetic basis not only to support the recent claim that L. friendi bouchei should be elevated to species rank (L. bouchei Zicsi and Csuzdi 1999), but also to conclude that L. rubellus friendoides is a valid species too, deserving a new name (L. heracleus stat. nov.). In addition, the AFLP results indicated the existence of a high cryptic diversity within L. friendi populations, which lacked geographic structure, resulting in the French samples being genetically closer to those from Ireland and Wales than to the Spanish ones. Our findings further highlight the likelihood that L. friendi and L. bouchei might have been overlooked or confounded with L. terrestris/L. herculeus and question the reliability of L. friendi records reported in the literature and those deposited in museums and sequence libraries (we provide evidence that this seem to be the case with two examples). We therefore advocate for a better link between morphological diagnostic characters and molecular sequences and the taxonomical validation of museums' collections and sequence repositories.

Automated summary

This study aimed to investigate the genetic variation of Lumbricus friendi and related species, and discovered high cryptic diversity within L. friendi populations. The findings also supported the elevation of L. friendi bouchei and L. rubellus friendoides to independent species.