Phylogeny and species delimitation of North European Lumbricillus (Clitellata, Enchytraeidae). -Zoologica Scripta, 00, 000-000. The enchytraeid genus Lumbricillus comprises about 80 described species of clitellate worms, which are up to a few centimetres long, and they mostly inhabit the littoral zone of nontropical marine and brackish waters world-wide. The phylogeny of this genus is poorly studied, but previous work has suggested that Lumbricillus is a non-monophyletic group. In this study, species boundaries and the phylogeny of this genus is re-assessed using more than 300 DNA-barcoded specimens (using COI mtDNA), part of which was also sequenced for two additional mitochondrial and four nuclear molecular markers. Statistical and coalescent based applications were used for the delimitation of a total of 24 species, of which 20 were identified as belonging to 17 described morphospecies; one morphospecies was found to be a complex of four delimited species, and another four delimited species could not be matched with any described species. Furthermore, gene trees, concatenation and multispecies coalescent based species trees were estimated using Bayesian inference. The estimated phylogenies confirm a non-monophyletic Lumbricillus as L. semifuscus is clearly excluded from the genus. Furthermore, the placement of a monophyletic clade consisting of L. arenarius, L. dubius, and an unidentified species varies between analyses; they are either found as the sister-group to the genus Grania or as sister-group to the remaining Lumbricillus, where the latter relationship is supported by the multispecies coalescent, which we consider as the most reliable method.
The white worm Enchytraeus albidus Henle, 1837 (Clitellata, Enchytraeidae) is easy to keep in laboratory cultures, and has therefore been employed as a model organism in basic and applied biological research. Its natural habitat includes terrestrial composts and wrack beds on seashores. However, the name E. albidus is currently used for a complex of morphologically similar and closely related species. We here revise the components of the E. albidus species complex based on a sample of 100 Enchytraeus specimens from 56 sites, most of which are across Europe. These samples were DNA-barcoded for the mitochondrial COI gene. A subset of them was sequenced for the nuclear ITS2 and H3 markers. Six species were delimited with strong support by the COI and ITS2 gene trees, as well as by a multi-locus species delimitation analysis. These species are identified morphologically and described as E. albidus s. str. (with designation of a neotype); Enchytraeus moebii (Michaelsen, 1885); Enchytraeus albellus Klinth, Erséus and Rota, sp. nov., E. cf. krumbachi (Čejka, 1913), E. sp. 1 (unnamed), and Enchytraeus polatdemiri Arslan and Timm, 2018. The last-mentioned species is a soda lake specialist, whereas E. albidus s. str. is both terrestrial and marine littoral; all other species occur only in seashores. The phylogeny of this group was estimated using the multi-species coalescent model. Monophyly of the E. albidus complex was recovered. Within this complex, three groups were recovered as monophyletic, but the relationship between them is unclear. One group comprises E. albidus s. str., E. albellus, and E. moebii; the second group E. cf. krumbachi and the unnamed E. sp. 1, and the third consists of only E. polatdemiri. This study serves as a framework for genetic identification of white worms used for experimental purposes.
Lumbricillus is a genus of clitellate worms with about 80 described species that inhabit marine and limnic habitats. This study follows a recent analysis of the phylogeny of the genus based on 24 species of Lumbricillus collected mainly in Norway and Sweden. We provide the illustrated taxonomic descriptions of all these species and describe two of them as new; Lumbricillus latithecatus sp. n. and L. scandicus sp. n. Using the recent phylogeny, we informally divide Lumbricillus into five distinct morphological groups, into which we also tentatively place the Lumbricillus species not included in this study. Furthermore, we establish Claparedrilus gen. n., with the type species C. semifuscoides sp. n., and transfer Pachydrilus semifuscus Claparède, 1861 (previously referred to Lumbricillus) into said genus.
DNA barcoding is an invaluable tool to identify clitellates, regardless of life stage or cryptic morphology. However, as COI (the standard barcode for animals) is relatively long (658 bp), sequencing it requires DNA of high quality. When DNA is fragmented due to degradation, alternative barcodes of shorter length present an option to obtain genetic material. We attempted to sequence 187 clitellates sampled from springs in Iceland. However, the material had been stored at room temperature for two years, and DNA of the worms had degraded, and only three COI sequences were produced (i.e., <2% success rate). Using two alternative barcodes of 16S (one ca. 320 bp, the other ca. 70 bp long) we increased the number of sequenced specimens to 51. Comparisons of the 16S sequences showed that even the short 70 bp fragment contained enough genetic variation to separate all clitellate species in the material. Combined with morphological examinations we recognized a total of 23 species, where at least 8 are new records for Iceland, some belonging to genera new for Iceland: Cernosvitoviella and Pristina. All the new taxa are included in an updated species list of Icelandic Clitellata. The material revealed some stygophilic species previously known to inhabit springs, but true stygobionts, which are restricted to groundwater habitats, were not found. Our study shows that short 16S fragments can be obtained from DNA too degraded to be used in traditional COI barcoding, and contain enough genetic variation to separate closely related clitellate species.
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