Phylogenetic systematisation and catalogue of paraphyletic “Rhabditidae” (Secernentea, Nematoda)
Keywords: Bauplan, Buetschlinema, Cooperia, checklist, description rate, genus, Litoditis, Lumbricicola, Macramphis, paraphylum, Porrocaecum, Reiterina, rejection of categories, Rhabdiasidae, Rhabditina, taxonomy
AbstractThis contribution presents an alphabetical list of 38 genus taxa accepted for “Rhabditidae” along with their synonyms and a list of the valid species that have been described to date with synonyms and specific type locality and habitat. Also names of misidentified species are given as synonyms if they can be assigned to a definite species. There are 492 species names, of which 368 are accepted as valid and 124 as synonyms, four of these being nomina oblita, whereas 37 species formerly described as “Rhabditidae” are transferred to taxa in other groups. Many nomenclatural changes are proposed. New combinations are established for 64 species names, 11 species names are suggested as new synonyms, and several previous synonymies are rescinded, particularly where it has been found an underlying complex of cryptic species (e.g. in Cruznema and Litoditis). Future analyses with new isolates will show if these species are valid or not. In Rhabditis macrospiculata, Pelodera operosa and Rhabditis teroides holotype and paratype of different sex belong to different species. Four species of Agamonema and Agamonematodum could not be properly allocated generically. The three new genus taxa Buetschlinema gen. n., Litoditis gen. n. and Reiterina gen. n. are constituted, and two new species names are proposed, namely Teratorhabditis geraerti nom. nov. for Teratorhabditis dentifera apud Zeidan and Geraert (1990), nec Völk (1950) and Crustorhabditis transita nom. nov. for Rhabditis scanica apud Sudhaus (1974c), nec Allgén (1949). Of the here suppressed genus names, Phasmarhabditis Andrássy, 1976 should be mentioned as a junior synonym of Pellioditis Dougherty, 1953. As new subjective synonyms, Evaginorhabditis Sultan, Kaul & Chhabra, 1985 is regarded as synonymous of Panagrolaimus Fuchs, 1930; Lumbricicola Friedlaender, 1895 of Porrocaecum Raillet
& Henry, 1912; and Macramphis Altherr, 1950 of Cooperia Ransom, 1907. A list of 35 nomina nuda is given. Type localities of most valid species are in European countries (42%). Currently, about four new species are described per year. As many more species await discovery, some suggestions for future taxonomic works are provided based on the experience of forty years. “Rhabditidae” are treated here as a paraphyletic group within the Rhabditina because Diplogastridae, Strongylida, Agfa/ Angiostomatidae, Rhabdiasidae and two other parasitic taxa arose from within this group and have sister taxa that
belong to “Rhabditidae”. There are good reasons to accept this paraphyletic taxon because it has well-defined ecology and morphology and allows making generalisations. Here, characteristics of the bauplan of “Rhabditidae” are specified. The species are mostly inhabitants of ephemeral terrestrial habitats rich in bacteria, but some are parasites of insects, gastropods, rodents and perhaps other mammals. With focus on common ancestry and not on distinguishing characters, a new systematisation for the genus taxa in “Rhabditidae” is suggested that is based primarily on the “New York” phylogenetic tree (Kiontke et al., 2007). Of the 72 existing genus and subgenus names of “Rhabditidae”, 38 genus names are accepted on phylogenetic arguments and nine new synonyms are suggested. Most of these genus taxa are monophyletic; however, no morphological apomorphy could be demonstrated for four of them, namely Haematozoon, Pelodera, Rhabditis and Rhabditoides. “Protorhabditis” is paraphyletic. Eight genus taxa are presently monotypic, and other eight still have an uncertain position in the system (incertae sedis). Within the monophyletic Rhabditina, four species-rich clades above the genus level are proposed: Eurhabditis, Pleiorhabditis (including Rhabdiasidae), Anarhabditis and Synrhabditis (including Agfa/ Angiostomatidae), the latter two names being new. Arguments are given why contrary to traditional systematics, no special rank (category) is assigned to these and other high-rank taxa. The genus is the only exception because a genus name is part of the species name.