A new isolate of Mesorhabditis monhystera (Butschli, 1873) Dougherty, 1955 (Rhabditida: Rhabditidae): re-evaluated with molecular data and scanning electron microscopic observations

A new isolate of Mesorhabditis monhystera (Butschli, 1873) Dougherty, 1955 is described and illustrated with morphological and molecular data. The phylogenetic analysis based on the D2/D3 segment of 28S rDNA using the Bayesian inference method, revealed monophyly of the genus Mesorhabditis as the subordinate taxa clustered in one clade. The clade further divided into two subclades representing the Monhystera-group and Spiculigera-group with 100% posterior probability values. However, GenBank sequences of several species constituting the Monhystera-group, showed high similarity and very little genetic divergence (98-99%) of up to 4-5 bases. In order to ascertain the status of those isolates, detailed morphological comparison is provided along with a pictorial key. A sequence-based phylogeography of haplogroups of Mesorhabditis using the median-joining network method, was also inferred. The results suggested the need for morphological validation of a species before its sequences are deposited in GenBank.

Automated summary

A new isolate of Mesorhabditis monhystera is described and illustrated using both morphological and molecular data. Phylogenetic analysis revealed that Mesorhabditis is a monophyletic genus, with subordinate taxa clustered in one clade. The clade further divided into two subclades, representing the Monhystera-group and Spiculigera-group. However, GenBank sequences of several species in the Monhystera-group showed high similarity and minimal genetic divergence.