Phylogenetic Relationships within the Nematode Subfamily Phascolostrongylinae (Nematoda: Strongyloidea) from Australian Macropodid and Vombatid Marsupials

Abstract

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.

Torquenema n. g., Wallabicola n. g., and Macropostrongyloides phascolomys n. sp.: New Genera and a New Species of Nematode (Strongylida: Phascolostrongylinae) Parasitic in Australian Macropodid and Vombatid Marsupials

“…The present study described two new genera and a new species from the subfamily Phascolostrongylinae supporting previous molecular evidence [ 3 , 5 , 17 ]. Future studies utilising the nuclear and mitochondrial DNA sequence data could provide better insights into the evolution of this highly diverse group of parasitic nematodes from herbivorous Australian marsupials.…”

“…sp., which is restricted to V. ursinus . The new genera and species described here are supported by previous molecular data [ 3 , 5 ].…”

“…Representative DNA sequences: Ribosomal DNA first and second internal transcribed spacers sequences (Genbank Accession MT396206) from M. giganteus , Research, Victoria, Australia [ 3 ].…”

“…Similar patterns have been observed in Macropostrongyloides mawsonae from M. giganteus which is predominantly encountered in the southern region of Australia but rarely detected in the northern part of Australia despite the continuous distribution of the host [ 10 ]. Previous molecular studies [ 3 , 5 ] have indicated genetic differences between specimens of W. dissimilis from Queensland and those collected from Victoria. No morphological differences were detected between these two genotypes in the current study, but the existence of a cryptic species cannot be eliminated.…”

“…A recent molecular study based on the first and second internal transcribed spacers (ITS-1 and ITS-2) of the nuclear ribosomal DNA revealed that the genera Macropostrongyloides and Paramacropostrongylus were paraphyletic, with Macropostrongyloides dissimilis Johnston and Mawson, 1939 and Paramacropostrongylus toraliformis Beveridge and Mawson, 1978 distinct from their respective congeners [ 3 ]. The study found that M. dissimilis , a dark-red nematode from the stomach of the swamp wallaby Wallabia bicolor (Desmarest) is a sister taxon to the only other stomach-inhabiting phascolostrongyline species Paramacropostrongylus typicus Johnston and Mawson, 1940 and Paramacropostrongylus iugalis Chilton, Beveridge and Andrews, 1993 from grey kangaroos [ 3 ].…”