An 18S rDNA Perspective on the Classification of Criconematoidea


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Journal of Nematology

Society of Nematologists

Subject: Life Sciences


ISSN: 0022-300X
eISSN: 2640-396X





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VOLUME 49 , ISSUE 3 (September 2017) > List of articles

An 18S rDNA Perspective on the Classification of Criconematoidea


Keywords : 18S rDNA, classification, criconematidae, phylogeny, systematics, taxonomy

Citation Information : Journal of Nematology. Volume 49, Issue 3, Pages 236-244, DOI:

License : (CC BY 4.0)

Received Date : 20-April-2017 / Published Online: 03-December-2017

Open Access article funded by National Science Foundation



In the nematode family Criconematidae, a taxonomy primarily based on cuticle characters has created classifications that are notoriously volatile. Molecular characters may lead to their stabilization. A phylogenetic tree of Criconematoidea was constructed using 166 new near full-length 18S rDNA sequences and 58 sequences from GenBank. Bayesian and maximum likelihood (ML) analyses produced trees with similar topologies. Major features include a strongly supported clade that includes Criconematidae and Hemicycliophoridae, excluding Paratylenchidae and Tylenchulidae. Another well-supported clade groups Criconema, Ogma, Crossonema, and Hemicriconemoides plus Xenocriconemella, combining nematodes with cuticular scales with those without scales at any life stage.

Mesocriconema, Discocriconemella limitanea, Hemicaloosia, and Lobocriconema are recognized as monophyletic groups, but Criconemoides is paraphyletic. Both trees support an unexpected sister relationship between Bakernema and Hemicycliophora. The 18S rDNA dataset was insufficient for distinguishing genus boundaries between Criconema, Ogma, and Crossonema. The relationships depicted by the 18S rDNA phylogeny suggest that key morphological characters used in the classification of Criconematidae are not homologous.

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