Perspectives in Earthworm Molecular Phylogeny: Recent Advances in Lumbricoidea and Standing Questions

Abstract

Earthworm systematics have been limited by the small number of taxonomically informative morphological characters and high levels of homoplasy in this group. However, molecular phylogenetic techniques have yielded significant improvements in earthworm taxonomy in the last 15 years. Several different approaches based on the use of different molecular markers, sequencing techniques, and compromises between specimen/taxon coverage and phylogenetic information have recently emerged (DNA barcoding, multigene phylogenetics, mitochondrial genome analysis, transcriptome analysis, targeted enrichment methods, and reduced representation techniques), providing solutions to different evolutionary questions regarding European earthworms. Molecular phylogenetics have led to significant advances being made in Lumbricidae systematics, such as the redefinition or discovery of new genera (Galiciandrilus, Compostelandrilus, Vindoboscolex, Castellodrilus), delimitation and revision of previously existing genera (Kritodrilus, Eophila, Zophoscolex, Bimastos), and changes to the status of subspecific taxa (such as the Allolobophorachaetophora complex). These approaches have enabled the identification of problems that can be resolved by molecular phylogenetics, including the revision of Aporrectodea, Allolobophora, Helodrilus, and Dendrobaena, as well as the examination of small taxa such as Perelia, Eumenescolex, and Iberoscolex. Similar advances have been made with the family Hormogastridae, in which integrative systematics have contributed to the description of several new species, including the delimitation of (formerly) cryptic species. At the family level, integrative systematics have provided a new genus system that better reflects the diversity and biogeography of these earthworms, and phylogenetic comparative methods provide insight into earthworm macroevolution. Despite these achievements, further research should be performed on the Tyrrhenian cryptic complexes, which are of special eco-evolutionary interest. These examples highlight the potential value of applying molecular phylogenetic techniques to other earthworm families, which are very diverse and occupy different terrestrial habitats across the world. The systematic implementation of such approaches should be encouraged among the different expert groups worldwide, with emphasis on collaboration and cooperation.

OTU Delimitation with Earthworm DNA Barcodes: A Comparison of Methods

“…Molecular approaches are increasingly used in the field of biodiversity sciences. In earthworm studies, DNA-based approaches have led to particularly significant advances in the fields of evolution and ecology [1]. The barcode region of the mitochondrial gene cytochrome c oxidase (COI) [2] is increasingly used to overcome the limitations of morphology-based identification [3].…”

Earthworms (Annelida: Oligochaeta, Lumbricidae) of the Kopaonik National Park (Serbia)

“…Dendrobaena alpina and D. byblica species groups show great taxonomic variability in pigmentation, the position of male pores, the position of calciferous diverticula, number of vesicles and the position of the spermathecal pores (CSUZDI et al, 2005;SZEDERJESI et al, 2017). MARCHÁN et al (2022) considered that although D. alpina alpina and D. byblica have been included in molecular phylogenetic analysis, further representatives of their wide taxonomic diversity in Eastern Europe remain to be studied, and the molecular markers must be standardized in order to combine the fragmentary data.…”

Earthworm Diversity and Distribution in Kathmandu, Bagmati Province, Central Nepal

“…Such a significant group of species lack intense taxonomic study on their diversity and distribution in Nepal (https://www.ksabmagar.com.np/2019/08/earthworms-ofnepal-brief-information.html). Marchan, (2022) has also emphasized on need of taxonomic proper delimitation of each taxon under the earthworm group along with number of unsolved contradictions among and in between the taxa (Ansari and Saywack, 2011). Thus, present study aimed to identify the local earthworm species along the northern and southern parts of Kathmandu district based on morphological features and figure out their distribution in different habitat.…”

“…the case of European, many Asian countries and global scale (Orgiazzi, 2016;Phillips, 2019;Mishra and Samal, 2021;Marchan, 2022). Knowing exact earthworm species diversity in the community, provides better alternatives according to need and accessibility of organism in particular area for particular waste types (Mishra and Samal, 2021).…”