Propappidae, Coates, 1986

Erséus, Christer, Williams, Bronwyn W., Horn, Kevin M., Halanych, Kenneth M., Santos, Scott R., James, Samuel W., Châtelliers, Michel Creuzé des & Anderson, Frank E., 2020, Phylogenomic analyses reveal a Palaeozoic radiation and support a freshwater origin for clitellate annelids, Zoologica Scripta 49 (5), pp. 614-640 : 633

4.3.3 | Propappidae and Enchytraeidae

The freshwater genus Propappus Michaelsen, 1905 was initially regarded as a ‘primitive’ member of Enchytraeidae , but several of its morphological features (chaetae with bifid tips, glands associated with chaetae, spermathecae in segment IV, thickened vasa deferentia in XII and ovaries in XIII% were considered different enough to justify its elevation to a monotypic family, Propappidae , by Coates (1986 %. Gustavsson, Ferraguti, & Marotta, (2008% found support for these families being closely related after studying the cuticular ultrastructure and spermatozoa of Propappus , but Gorgón, Krodkiewska and Światek (2015 % found the ovary ultrastructure and oogenesis of this genus similar to those known for other aquatic clitellates and clearly different from corresponding features in Enchytraeidae . In the first molecular studies involving Propappus , both Erséus and Källersjö (2004 % and Rousset et al. (2007 % found Propappus to be sister to Haplotaxis , but with low support. The Propappidae + Enchytraeidae group was, however, recovered by Marotta et al. (2008: Figure 3%, but again with low support. The long branch of Propappus in our tree (Figure 1% manifests a genetic gap between Propappidae and Enchytraeidae , and our analyses sometimes place Propappus as sister to a clade comprising Enchytraeidae, Lumbriculata and Metagynophora (along with some haplotaxids% (Figures 2 and 3 and Figure S3; Supplementary Materials%.

Enchytraeidae is a large family with species from both terrestrial and aquatic habitats. Its monophyly was verified, and its internal phylogeny was analysed, by Erséus, Rota, et al. (2010% and Martinsson, Dózsa-Farkas, Rota, and Erséus (2017 %. In our tree, the ingroup topology (i.e. with Grania nearest to Enchytraeus % conforms better with the tree of Martinsson et al. than with Erséus et al.’s results, where Grania is nearer to Mesenchytraeus than to Enchytraeus . However, with ca. 700 enchytraeid species (in ca. 30 genera% worldwide, it is possible that the six species we sampled, representing only four genera, are not enough to robustly resolve the relationships within this family.

Our results suggest that either a clade comprising Propappidae and Enchytraeidae , or Enchytraeidae alone, is sister to all the remaining groups discussed below. This refutes a previous hypothesis that enchytraeids are closely related to earthworms, that is, Metagynophora (see Erséus, 2005 %.