The best is yet to come: six new species within a large-bodied earthworm genus (Scherotheca, Lumbricidae) in a densely sampled region (south-western France)

Abstract

Since the 18th century, several taxonomists have contributed to knowledge of the French earthworm fauna, one of the best-known earthworm communities in Europe, with 164 species currently described. Surprisingly, new species keep being added constantly, even large ones, which are usually the first to be described. The recent discovery of six undescribed morphospecies of Scherotheca during a sampling survey in southern France suggests that other large Lumbricidae remain to be discovered. We provide here an integrative description of these six species, Scherotheca albina Marchán & Decaëns sp. nov., Scherotheca betharramensis Marchán & Decaëns sp. nov., Scherotheca microthomasi Marchán & Decaëns sp. nov., Scherotheca shaihulud Marchán & Decaëns sp. nov., Scherotheca etcheberryensis Marchán & Decaëns sp. nov. and Scherotheca trezencensis Marchán & Decaëns sp. nov., formally name them and place them in a molecular phylogenetic framework together with their Scherotheca relatives from south-western France. This increases the diversity of Scherotheca to 51 species, including Scherotheca haymozi comb. nov. as a small-sized representative of the genus. The validity of the elevation of several subspecies to specific status was corroborated by molecular phylogenetic evidence, and previously unknown cryptic speciation within Scherotheca was detected. Two geographically coherent clades (roughly matching Nouvelle-Aquitaine and Occitanie) correspond to two existing subgenera. The unusually high taxonomic and morphological diversity of Scherotheca within the Pyrénées-Atlantiques may be related to biotic interactions, climatic factors and historical causes. These features highlight the importance of the conservation of these unique earthworm species.