Deceptive morphological variation in Hirschmanniella mucronata (Nematoda: Pratylenchidae) and a polytomous key to the genus

Hirschmanniella mucronata populations isolated from two Cambodian provinces were characterised using morphological, morphometric and molecular criteria. Examination of 1024 specimens from 60 different paddy fields revealed high intraspecific variation in morphology and morphometrics, especially in tail terminus shape and stylet length. Sequence results confirmed that morphologically divergent individuals represent a single species, suggesting that neglecting morphological variation has led to an overestimation of Hirschmanniella diversity in former studies. Phylogenetic analysis of the SSU, D2-D3, LSU and ITS1-5.8S-ITS2 regions revealed three concordant clades, H. mucronata having a sister relationship with H. kwazuna and H. loofi . Plotting the diagnostic features, including tail terminus shape, stylet length and lip region morphology on the phylogenetic framework, revealed that none of them supported the clades and represented convergent features. All three molecular markers were able to discriminate all Hirschmanniella species, but the D2-D3 region was the easiest, fastest and most successful region to be amplified. Species delimitation and the diagnostic features of Hirschmanniella were re-evaluated. Hirschmanniella abnormalis and H. exacta are considered to be junior synonyms of H. oryzae and H. mannai a species inquirenda . Finally, a list of valid species with indication of synonyms and a polytomous key are provided.