Data from: Cryptic diversity in the well-studied terrestrial worm Cognettia sphagnetorum (Clitellata: Enchytraeidae)

The terrestrial worm Cognettia sphagnetorum has been used as a model in
several studies focusing on research areas such as climate change as well
as forest and soil ecology; it has also been shown to play a key role in
the decomposition of organic matter and nutrient cycling. Cognettia is an
enchytraeid genus commonly found in acidic terrestrial habitats, such as
coniferous forests and bogs. In this study, the diversity of the genus,
with particular focus on the morphospecies C. sphagnetorum in northern
Europe, is assessed using four molecular markers, the mitochondrial COI
(cytochrome c oxidase subunit I) and16S (16S ribosomal RNA), and the
nuclear H3 (Histone 3) and ITS (Internal Transcribed Spacer). The datasets
were first delimited into Molecular Operational Units (MOTUs) and the
existence of global barcoding-gaps was tested. Single gene-trees were then
estimated for all genes using Bayesian Inference, and a species tree was
estimated with all markers combined using the multi-species coalescence.
The results show that in northern Europe the genus consists of at least
eight MOTUs supported by all genes except H3. Four of these MOTUs were
within the morphotaxon C. sphagnetorum and two within Cognettia
glandulosa. C. sphagnetorum s.l. was found to be non-monophyletic in all
gene-trees, as well as in the species tree. As the MOTUs were well
separated and non-monophyly was observed within C. sphagnetorum s.l., we
conclude that the MOTUs are best treated as separate species. Given that
cryptic diversity was found in this genus, we recommend that material of
Cognettia used in future studies should be identified using molecular
barcodes.