Nematode biodiversity assessments need vouchered databases: A BOLD reference library for plant-parasitic nematodes in the superfamily Criconematoidea.

Nematodes are frequently cited as underrepresented in faunistic surveys using DNA barcoding with COI. This underrepresentation is generally attributed to a limited presence of nematodes in DNA databases which, in turn, is often ascribed to structural variability and high evolutionary rates in nematode mitochondrial genomes. Empirical evidence, however, indicates that many taxa are readily amplified with primer sets specifically targeted to different nematode families. Here we report the development of a COI reference library of 1726 specimens in the terrestrial plant parasitic nematode superfamily Criconematoidea. Specimens collected during an ecoregion survey of North America were individually photographed, measured, and PCR amplified to produce a 721 bp region of COI for taxonomic analysis. A neighbor-joining tree structured the dataset into 179 haplotype groups that generally conformed to morphospecies in traditional analysis or Barcode Index Numbers (BINs) in the BOLD system, although absent formal BIN membership due to insufficient overlap with the Folmer region of COI. Approximately one-third of the haplotype groups could be associated with previously described species. The geographic distribution of criconematid nematode species suggests a structure influenced by the major habitat types in the United States and Canada. All sequences collected in the ecoregion survey are deposited in BOLD.

Morphological and molecular characterization of Discocriconemella inarata, an endemic nematode from north american native tallgrass prairies.

Discocriconemella inarata, a plant parasitic nematode species originally discovered in a virgin tallgrass prairie in northwest Iowa, was re-examined by molecular and morphological analyses of topotype material. This species has never been recorded in cultivated fields and could potentially serve as an indicator for high quality prairie habitats. DNA sequence from a conserved 3' portion of the 18S ribosomal gene exhibited an identical match between D. inarata topotype specimens and topotype specimens of Mesocriconema xenoplax from Fresno, California. Higher resolution sequence analyses using the internal transcribed spacer 1 (ITS1) and a portion of the mitochondrial gene cytochrome b (cytb) allowed discrimination of D. inarata apart from M. xenoplax. This pair of species formed a well-supported clade with other Mesocriconema species exclusive of tropical Discocriconemella species. Scanning electron microscopy confirmed the absence of submedian lobes on D. inarata, suggesting a secondary loss of this defining morphological characteristic for Mesocriconema. Observations and measurements of D. inarata juveniles were added for the first time. Surveys of other prairies within the Great Plains expanded the known distribution of this species.