Comparison of Biological, Molecular, and Morphological Methods of Species Identification in a Set of Cultured Panagrolaimus Isolates

We have developed a molecular barcode system that uses the small subunit ribosomal RNA (SSU) sequence to define molecular operational taxonomic units (MOTU) of soil nematodes. Here we attempt to differentiate five cultured isolates of a taxonomically difficult genus, Panagrolaimus, using morphological, molecular, and biological (breeding) criteria. The results indicated that the five culture populations belonged to two reproductively isolated species. The available morphological criteria, including scanning electron microscopy (SEM), were insufficient to differentiate among them, and all five could be classified as one morphospecies. Within-culture variation of the morphometrical data did not discern between the two biological species. Sequence data clearly separated the populations into two groups that supported the breeding results. Given this study represented only five populations of one genus, we suggest a congruence of MOTU analysis with the biological species concept. This multifaceted approach is promising for future identification of nematodes as it is simple, comparable, and transferable

Nematodes from extreme freshwater habitats

Hodda M, Ocana A, Traunspurger W. Nematodes from extreme freshwater habitats. In: Abebe E, Andrassy I, Traunspurger W, eds. Freshwater Nematodes: Ecology and taxonomy. Wallingford: CAB International; 2006: 752

Freshwater nematodes in environmental science

Hoess S, Zullini A, Traunspurger W. Freshwater nematodes in environmental science. In: Abebe E, Andrassy I, Traunspurger W, eds. Freshwater Nematodes: Ecology and taxonomy. Wallingford: CAB International; 2006: 752

Defining operational taxonomic units using DNA barcode data

The scale of diversity of life on this planet is a significant challenge for any scientific programme hoping to produce a complete catalogue, whatever means is used. For DNA barcoding studies, this difficulty is compounded by the realization that any chosen barcode sequence is not the gene ‘for’ speciation and that taxa have evolutionary histories. How are we to disentangle the confounding effects of reticulate population genetic processes? Using the DNA barcode data from meiofaunal surveys, here we discuss the benefits of treating the taxa defined by barcodes without reference to their correspondence to ‘species’, and suggest that using this non-idealist approach facilitates access to taxon groups that are not accessible to other methods of enumeration and classification. Major issues remain, in particular the methodologies for taxon discrimination in DNA barcode data