Unravelling cryptic diversity in the Paratrichodorus allius-group species complex to resolve eight new species of the genus and new insights on the molecular phylogeny (Nematoda: Trichodoridae)

The stubby-root nematode genus Paratrichodorus comprises species of plant polyphagous ectoparasitic nematodes distributed worldwide and a few of them are plant virus-vectors (tobravirus). This is one of the most difficult nematode genera in terms of species identification, since it is phenotypically conserved with closely related species and is highly sensitive to the specimen fixation and preservation processes. Using an integrative and multidisciplinary taxonomy framework, we determined species boundaries among the Paratrichodorus populations from a P. allius species-complex sampled in cultivated and natural ecosystems across Spain. We support the hypothesis that nematode diversity of the P. allius species-complex remains underestimated and describe here a total of eight new species on the basis of detailed morphological and molecular characterization of 16 Paratrichodorus populations: Paratrichodorus asidonaensis sp. nov., Paratrichodorus benalupensis sp. nov., Paratrichodorus hinogerus sp. nov., Paratrichodorus litoralis sp. nov., Paratrichodorus paraallius sp. nov., Paratrichodorus rocianerus sp. nov., Paratrichodorus tarifaensis sp. nov., and Paratrichodorus uliaensis sp. nov. This study emphasizes the importance of properly applying a broad taxonomic framework in plant-parasitic nematodes. It is also relevant for plant health, since it correctly delimits species morphologically closed to the virus vector nematode, P. allius, and gives proper molecular markers for its unequivocal identification.