Multigene phylogeny reveals a new Iranian earthworm genus (Lumbricidae: Philomontanus) with three new species

Barcode gap delimitation and phylogenetic analyses in integrative earthworm taxonomy: Dendrobaena byblica complex

Dendrobaena byblica (Rosa, 1893) is a species complex consisting of at least 17 nominal taxa and with Circum-Mediterranean distribution. The taxonomic classification of this group based on shape of internal structures and external characteristics indicated that this species complex indeed consists of several clades. More molecular studies are needed to confirm this issue. In this study, samples from the Hyrcanian forests in the north of Iran were studied, which were genetically different from the sequences retrieved from GenBank. The results of the ABGD analyses suggest that the genetic distance for species delimitation in D. byblica is 9%, a much lower value than that reported for other species included in the family Lumbricidae. The range of COI K2p genetic distance between GenBank sequences of Dendrobaena and examined species in the present study, is 12.3-24.6%. Assessing whether these genetic variations correspond to different biological species or correspond to intraspecific phenotypic variability will require further studies using other genetic molecular markers.

Global species delimitation of the cosmopolitan marine littoral earthworm Pontodrilus litoralis (Grube, 1855)

The marine littoral earthworm Pontodrilus litoralis (Grube, 1855) is widely distributed and is reported as a single species. This study utilized an integrative taxonomic approach based upon morphological examination, phylogenetic reconstruction, and molecular species delimitation, to test whether the taxon is a single species or a species complex. For this, a total of 114 P. litoralis specimens collected from North America, Africa, Australia and Oceania, Europe and Asia were used. The phylogenetic analyses revealed deeply divergent mitochondrial lineages and a high level of genetic diversity among P. litoralis populations. Both single and multi-locus species delimitation analyses yielded several molecular operational taxonomic units. Therefore, due to the homogeneity of morphological characteristics, it is likely that the morphospecies P. litoralis is a complex of four or more cryptic species, suggesting that more sampling is required and that the population structure genetic data and gene flow need to be investigated.

Investigating the impacts of agricultural land use on soil earthworm communities: A case study of northern Zagros Mountains of Iran

Earthworms play a crucial role in the invertebrate community of soil by contributing to the belowground biomass and biogeochemical cycle. Environmental stresses, such as human activities and land use changes, have been found to negatively affect their abundance and diversity. To investigate the impact of agricultural land use and pastures on earthworms' genetic diversity in the Northern Zagros Mountains, we used COI molecular marker and DNA barcoding approaches. We collected earthworm specimens from four farmland sites and six pastures and assessed the abundance and species composition of earthworm communities across the two land uses using quadrat sampling. Using the barcoding method, we identified 13 molecular operational taxonomic units (MOTUs) among the captured earthworms. Our results showed that the number of total MOTUs, density, and earthworm communities differed significantly between the two land uses. We also found that pastures had more abundant earthworms, while farmlands had greater diversity. The diversity of OTUs in the Lumbricidae family was dominant in the agricultural system. Overall, the population of invasive earthworm species in cultivation systems is influenced by chemical inputs and organic materials from plant residues, cover crops, manure, or organic fertilizers. Given the rapid rate of land use change worldwide, especially in Iran, it is crucial to understand the impact of disturbances on earthworms.

The threat of a non-native oligochaete species in Iran's freshwater: assessment of the diversity and origin of Eiseniella tetraedra (Savigny, 1826) and its response to climate change

Oligochaetes are the most abundant benthic taxa in aquatic ecosystems that play an important role in food webs. The present study aims to assess the diversity and origin of Eiseniella tetraedra as a non-native species in the Lar National Park of Iran and also its response to current and future climate change. We obtained the specimen from rivers and sequenced the mitochondrial gene Cytochrome Oxidase subunit I (COI) and combined them with 117 sequences from the Jajroud and Karaj rivers in Iran and native regions from GenBank (NCBI). We also ran Species Distribution Modelings (SDMs) using an ensemble model approach that was estimated according to two shared socio-economic pathways (SSPs): 126 and 585 of the MRI-ESM2 based on CMIP6. According to the results, all the samples examined in the current study originated from Spanish rivers, and no unique haplotype was found in the Lar National Park. Moreover, the results also show high haplotype diversity that can positively affect the success of this non-native species in different freshwater. Also, the results of SDMs depict that climate change would remarkably affect the distribution of E. tetraedra and it verifies the invasion power of E. tetraedra in Iran's freshwater ecosystems over time.

Catch-All No More: Integrative Systematic Revision of the Genus Allolobophora Eisen, 1874 (Crassiclitellata, Lumbricidae) with the Description of Two New Relict Earthworm Genera

The taxonomy of earthworms has been riddled by instability, lack of systematically useful characters, and lax diagnoses of some genera. This has led to the use of some genera such as Allolobophora Eisen, 1874 as taxonomic wastebaskets, blurring their evolution and biogeographical history. The implementation of molecular techniques has revolutionized the systematics of the genus; however, some of its species have not been previously included in molecular phylogenetic analyses. Thus, the molecular markers COI, 16S, ND1, 12S, and 28S were sequenced for six endemic species including several taxa of Allolobophora and Aporrectodea Örely, 1885 (another related catch-all genus). Phylogenetic relationships determined by Bayesian inference and maximum likelihood analyses support the status of two of the six taxa examined (Allolobophora burgondiae Bouché, 1972 and Aporrectodea icterica Savigny, 1826) as part of Allolobophora sensu stricto and a presumed synonymy between Allolobophora and Heraclescolex Qiu and Bouché, 1998. Branch lengths and average pairwise genetic distances support the transfer of Allolobophora satchelli Bouché, 1972 to the genus Panoniona Mršić and Šapkarev, 1988 and the emergence of two new genera, Heraultia gen. nov. and Vosgesia gen. nov., endemic to France, hosting Allolobophora tiginosa Bouché, 1972 and Allolobophora zicsii Bouché, 1972, respectively. The aforementioned changes of status and the diagnosis for Heraultia and Vosgesia are presented. These results provided more evolutionarily and biogeographically coherent earthworm groups and highlighted that the Maghreb and the area around the Alps are potential key locations for the diversification of Allolobophora and several lineages of Lumbricidae.

Sokefun, Yadav S. Disentangling earthworm taxonomic stumbling blocks using molecular markers

Taxonomic classification of earthworms based on anatomical features has created several challenges for systematics and population genetics. This study examines the application of molecular markers, in particular mitochondrial cytochrome oxidase (COI), to facilitate discrimination of closely related earthworm species. Molecular markers have also provided insights into population genetics by aiding assessment of genetic diversity, lineage sorting, and genealogical distributions of populations for several species. Phylogeography—a study that evaluates the geographical distribution of these genealogical lineages and the role of historical processes in shaping their distribution—has also provided insights into ecology and biodiversity. Such studies are also essential to understand the distribution patterns of invasive earthworm species that have been introduced in non-native ecosystems globally. The negative consequences of these invasions on native species include competition for food resources and altered ecosystems. We anticipate that molecular markers such as COI and DNA barcoding offer potential solutions to disentangling taxonomic impediments in earthworms and advancing their systematics and population genetics. 

Sorry atlanticus, you are not my type: molecular assessment splits Zophoscolex (Lumbricidae: Crassiclitellata) into French and Iberian genera

Molecular phylogenetics contributes to making important advances in the challenging field of earthworm taxonomy. Use of this type of analysis has enabled clarification of the phylogenetic relationships between early-branching genera of Lumbricidae within the highly diverse Franco-Iberian realm. However, molecular phylogenetic studies of the genus Zophoscolex are scarce and have led to taxonomic uncertainty due to insufficient sampling and the absence of the type species, Z. atlanticus, from such studies. The present study investigated 11 species of Zophoscolex (including Z. atlanticus), and the phylogenetic relationships were deduced from seven molecular markers (COI, COII, 16S, tRNAs, ND1, 12S, 28S) by Bayesian and maximum likelihood inference. The findings show that species of Zophoscolex did not belong to a single clade. Zophoscolex atlanticus was placed in a clade with Z. micellus, Z. graffi and Ethnodrilus zajonci. Other species of the genus were found to belong to the genera Cataladrilus and Compostelandrilus. Finally, most of the Iberian species form a distinct clade, which was formally described as the revised genus Castellodrilus. Based on these findings, Zophoscolex is restricted to French representatives. These results highlight the importance of incorporating type species in molecular phylogenetic analyses in order to reconcile taxonomy and systematics.