A revision of the minor species group in the millipede genus Nannaria Chamberlin, 1918 (Diplopoda, Polydesmida, Xystodesmidae)

Abstract

Millipedes in the family Xystodesmidae (Polydesmida) are often referred to as “colorful, flat-backed millipedes” for their bright aposematic coloration and tendency to form Müllerian mimicry rings in the Appalachian region. However, there are many species of Xystodesmidae that do not display colorful warning patterns, and instead have more cryptic appearances. Perhaps for this reason, groups such as the genus Nannaria have remained understudied, despite containing a large number of undescribed species. Before his death in 2012, R. L. Hoffman worked on a revision of the genus Nannaria, and synthesized material and drawings since 1949. Here the work is continued, inferring a molecular phylogeny of the Nannariini (Nannaria + Oenomaea pulchella), and revealing two clades within the genus. One clade is named the minor species group, and the second is the wilsoni species group. This revision, using a molecular phylogenetic framework, is the basis for descriptions of 35 new species in the minor species group. A multi-gene molecular phylogeny is used to make taxonomic changes in the taxon. Eleven putative species of Nannaria are also illustrated and discussed. Additionally, detailed collection, natural history and habitat notes, distribution maps, and a key to species of the Nannaria minor species group are provided. These items are synthesized as a basis for a revision of the genus, which hopefully will aid conservation and evolutionary investigations of this cryptic and understudied group.

A revision of the wilsoni species group in the millipede genus Nannaria Chamberlin, 1918 (Diplopoda, Polydesmida, Xystodesmidae)

“…This study showed that Oenomaea pulchella (Bollman, 1889) was sister to Nannaria, which was composed of two monophyletic species groups: the minor species group and the wilsoni species group. Means et al (2021b), with additional species sampling within the genus, confirmed the monophyly of these species groups, and described 35 new species of the minor species group.…”

“…Previous authors have indicated that many undescribed species, and possibly even genera, remain to be found in the tribe (Hoffman 1999;Hennen and Shelley 2015;Marek et al 2018), and this has been supported in a recent study of the minor species group, in which 35 new species of the genus were named (Means et al 2021b). However, the wilsoni species group has not been investigated, and new species have been uncovered by examination of material in museum collections.…”

“…After field collection of specimens, millipedes were processed using the workflow described by Means et al (2021b). Millipedes were photographed on a moss background in the laboratory with a Canon EOS 6D camera and a 50-mm lens.…”

“…The tribe Nannariini is diagnosed by the following main characters: sterna with lateral triangular spines; males with twisted, spatulate pre-gonopodal claws; gonopods with straight or curving acropodites; and a stout, long prefemoral process (Hoffman 1964;Hennen and Shelley 2015;Means et al 2021b: figs 2, 8). For a detailed summary of the taxonomic history and diagnostic characters of the Nannariini, see Means et al (2021b).…”

“…With the discovery of 52 undescribed species in the two groups, the ambitious goal of describing them all was split between two projects. The species of the minor species group were treated in a first revision (Means et al 2021b), while the species of the wilsoni species group are treated here. The aims of this study are to: (1) confirm the monophyly of the wilsoni species group using molecular phylogenetics, (2) describe new species of this species group, and (3) provide full taxonomic accounts for each species in the species group, including natural history notes and an investigation of the ecology of the species.…”