Background: The strongyloid nematode subfamily Phascolostrongylinae are parasites of the large intestine and stomach of Australian macropods (Macropodidae) and wombats (Vombatidae). Based on morphological classifications, the Phascolostrongylinae is comprised of seven genera belonging to three tribes (Phascolostrongylinea, Macropostrongyloidinea, and Hypodontinea). The phylogenetic relationships among the genera of the Phascolostrongylinae were tested using the first and second internal transcribed spacer (ITS+) sequences of the ribosomal DNA. Results: Monophyly was encountered in the tribe Phascolostrongylinea comprising two genera, Phascolostrongylus and Oesophagostomoides, found exclusively in the large intestine of wombats. The tribe Hypodontinea, represented by the genera Hypodontus and Macropicola from the ileum and large intestine of macropods was also found to be monophyletic, but with low support. The tribe Macropostrongyloidinea comprising the genera Macropostrongyloides and Paramacropostrongylus was paraphyletic with the species occurring in the stomach grouping separately to those found in the large intestines of their hosts. Finally, Macropostrongyloides dissimilis from the stomach of the swamp wallaby and Paramacropostrongylus toraliformis from the large intestine of the eastern grey kangaroo were distinct from their respective congeners. Conclusion: The current study provided strong support for the generic composition of the tribe Phascolostrongylinea and low support for the tribe Hypodontinea. However, the relationships within the tribe Macropostrongyloidinea are more complex and its monophyly was not supported by the current ITS+ dataset. The unexpected finding of M. dissimilis and P. toraliformis being distantly related to their respective congeners suggests a requirement for future taxonomic revision which may warrant separation of these species at the generic level.

The strongyloid nematodes belonging to the subfamily Phascolostrongylinae occur primarily in the large intestines of macropodid and vombatid marsupials. Current molecular evidence suggests that the two nematode species, Macropostrongyloides dissimilis and Paramacropostrongylus toraliformis, from macropodid marsupials are distant from their respective congeners. Furthermore, specimens of Macropostrongyloides lasiorhini from the large intestines of the southern hairy-nosed wombat (Lasiorhinus latifrons) and the common wombat (Vombatus ursinus) are genetically distinct. This study aimed to describe the new genera Torquenema n. g. (with T. toraliforme n. comb. as the type species) from the eastern grey kangaroo, Wallabicola n. g. (with W. dissimilis n. comb. as the type species) from the swamp wallaby and a new species Macropostrongyloides phascolomys n. sp. from the common wombat, using light and scanning electron microscopy.

The strongyloid nematode subfamily Phascolostrongylinae comprises parasites of the large intestine and stomach of Australian macropods and wombats. In this study, we tested the phylogenetic relationships among the genera of the Phascolostrongylinae using the first and second internal transcribed spacers of the nuclear ribosomal DNA. Monophyly was encountered in the tribe Phascolostrongylinea comprising two genera, Phascolostrongylus and Oesophagostomoides, found exclusively in the large intestine of wombats. The tribe Hypodontinea, represented by the genera Hypodontus and Macropicola from the ileum and large intestine of macropods, was also found to be monophyletic. The tribe Macropostrongyloidinea, comprising the genera Macropostrongyloides and Paramacropostrongylus, was paraphyletic with the species occurring in the stomach grouping separately from those found in the large intestines of their hosts. However, Macropostrongyloidesdissimilis from the stomach of the swamp wallaby and Paramacropostrongylus toraliformis from the large intestine of the eastern grey kangaroo were distinct from their respective congeners. This study provided strong support for the generic composition of the tribe Phascolostrongylinea. The unexpected finding of M. dissimilis and P. toraliformis being distantly related to their respective congeners suggests a requirement for future taxonomic revision that may warrant separation of these species at the generic level.

Nematodes of the genus Macropostrongyloides inhabit the large intestines or stomachs of macropodid (kangaroos and wallabies) and vombatid (wombats) marsupials. This study established the relationships of seven species of Macropostrongyloides using mitochondrial (mt) protein amino acid sequence data sets. Phylogenetic analyses revealed that species of Macropostrongyloides (M. lasiorhini, M. baylisi, M. yamagutii, M. spearei, M. mawsonae and M. woodi) from the large intestines of their hosts formed a monophyletic assemblage with strong nodal support to the exclusion of M. dissimilis from the stomach of the swamp wallaby. Furthermore, the mitochondrial protein-coding genes provided greater insights into the diversity and phylogeny of the genus Macropostrongyloides; such data sets could potentially be used to elucidate the relationships among other parasitic nematodes of Australian marsupials.

The genetic variation and taxonomic status of the four morphologically-defined species of Macropostrongyloides in Australian macropodid and vombatid marsupials were examined using sequence data of the ITS+ region (=first and second internal transcribed spacers, and the 5.8S rRNA gene) of the nuclear ribosomal DNA. The results of the phylogenetic analyses revealed that Ma. baylisi was a species complex consisting of four genetically distinct groups, some of which are host-specific. In addition, Ma. lasiorhini in the common wombat (Vombatus ursinus) did not form a monophyletic clade with Ma. lasiorhini from the southern hairy-nosed wombat (Lasiorhinus latifrons), suggesting the possibility of cryptic (genetically distinct but morphologically similar) species. There was also some genetic divergence between Ma. dissimilis in swamp wallabies (Wallabia bicolor) from different geographical regions. In contrast, there was no genetic divergence among specimens of Ma. yamagutii across its broad geographical range or between host species (i.e. Macropus fuliginosus and M. giganteus). Macropostrongyloides dissimilis represented the sister taxon to Ma. baylisi, Ma. yamagutii and Ma. lasiorhini. Further morphological and molecular studies are required to assess the species complex of Ma. baylisi.

Background The subfamily Phascolostrongylinae (Superfamily Strongyloidea) comprises nematodes that are parasitic in the gastrointestinal tracts of macropodid (Family Macropodidae) and vombatid (Family Vombatidae) marsupials. Currently, nine genera and 20 species have been attributed to the subfamily Phascolostrongylinae. Previous studies using sequence data sets for the internal transcribed spacers (ITS) of nuclear ribosomal DNA showed conflicting topologies between the Phascolostrongylinae and related subfamilies. Therefore, the aim of this study was to validate the phylogenetic relationships within the Phascolostrongylinae and its relationship with the families Chabertiidae and Strongylidae using mitochondrial amino acid sequences. Methods The sequences of all 12 mitochondrial protein-coding genes were obtained by next-generation sequencing of individual adult nematodes (n = 8) representing members of the Phascolostrongylinae. These sequences were conceptually translated and the phylogenetic relationships within the Phascolostrongylinae and its relationship with the families Chabertiidae and Strongylidae were inferred from aligned, concatenated amino acid sequence data sets. Results Within the Phascolostrongylinae, the wombat-specific genera grouped separately from the genera occurring in macropods. Two of the phascolostrongyline tribes were monophyletic, including Phascolostrongylinea and Hypodontinea, whereas the tribe Macropostrongyloidinea was paraphyletic. The tribe Phascolostrongylinea occurring in wombats was closely related to Oesophagostomum spp., also from the family Chabertiidae, which formed a sister relationship with the Phascolostrongylinae. Conclusion The current phylogenetic relationship within the subfamily Phascolostrongylinae supports findings from a previous study based on ITS sequence data. This study contributes also to the understanding of the phylogenetic position of the subfamily Phascolostrongylinae within the Chabertiidae. Future studies investigating the relationships between the Phascolostrongylinae and Cloacininae from macropodid marsupials may advance our knowledge of the phylogeny of strongyloid nematodes in marsupials. Graphical Abstract

A phylogenetic analysis of the genera of the strongyloid sub-family Cloacininae from macropodoid marsupials in Australasia was undertaken based on morphological characteristics and analysis of concatenated sequences (ITS+) of the first (ITS-1) and second (ITS-2) internal transcribed spacers of nuclear ribosomal DNA. Neither approach provided a robust phylogeny, but similarities between the two methods in terms of generic groupings suggested that substantial revision is needed of the current phenetic classification, with some of the key morphological characteristics currently used to define genera and tribes proving to be homoplasious.

No abstract