A strong backbone for an invertebrate group: anchored phylogenomics improves the resolution of genus-level relationships within the Lumbricidae (Annelida, Crassiclitellata)

Earthworm taxonomy has shown great instability across the twentieth century, as exemplified by the numerous genera system of Lumbricidae. Sanger-sequenced “legacy markers” have allowed to recover genus-level clades within Lumbricidae, but relationships between genera were often recovered as polytomies. Anchored hybrid enrichment (AHE) is a recent source for phylogenomic analyses, providing hundreds of unique orthologous loci from across the genome with several advantages (like informativeness across different taxonomic scales, cost-effectiveness, no necessity of special preservation protocols). In this work, AHE was applied to 31 Lumbricidae genera to validate recent genus-level changes and to provide a solid “backbone” for the systematics of the family. Five hundred ninety-four non-duplicated loci were sequenced, and phylogenomic inference was performed using the concatenated alignments and independent loci. A “legacy marker” dataset was used to study the effect of the inclusion of the AHE phylogenomic tree as constraint. Lumbricidae was recovered as a monophyletic family, with Diporodrilus pilosus as the earliest branching taxa, followed by two large clades The first one comprised the Franco Iberian genera Castellodrilus , Cataladrilus , Prosellodrilus , Zophoscolex , Ethnodrilus , Kritodrilus , Postandrilus , Galiciandrilus , and Compostelandrilus ; the Italian Pietromodeona ; and the Central European Vindoboscolex . The second one included the rest of the studied Lumbricidae genera, with relationships between them being well resolved and strongly supported. The phylogenomic backbone improved the topological resolution and support of the legacy marker phylogenetic tree. Thus, AHE proved highly suitable for phylogenomic inference in lumbricid earthworms and closely related taxa, allowing to propose changes to the above-genus-level systematics of the family.