Contribution to the knowledge of the genus Boucheona (Oligochaeta, Hormogastridae) in France with a newly described species and a redescribed species

Abstract

Hormogastrid earthworms are found in the diversity hotspot of the Franco-Iberian domain, together with the better-known family Lumbricidae. Integrative systematics (the combination of morphological, molecular and ecological data) have increased our knowledge of the diversity and evolutionary history of these earthworms, highlighting unresolved taxonomic conflicts. One example of a species group in need of integrative taxonomic revision is the genus Boucheona in France. In this work, we analyzed their diversity using previously published data together with additional data obtained from recently sampled localities. Molecular data including DNA barcodes and additional markers enabled us to reconstruct Bayesian and time-calibrated phylogenies to discuss the evolutionary relationships among the different taxa, and to propose hypotheses regarding their biogeographical history. Based on our results, four species of Boucheona are present in Southern France, including two new taxa. Morphological distinctness and molecular phylogenetics results supported the status of four populations as the newly described Boucheona corbierensis sp. nov., as well as the status of "Hormogaster pretiosa var. nigra" as an independent species, redescribed as Boucheona tenebrae sp. nov. These results provide a new perspective of the importance of the genus Boucheona in southern France, as the possible evolutionary origin of a clade of giant anecic earthworms with unknown (but probably remarkable) impact on ecosystem functioning across their range.