On the morphometric identity of populations of Helicotylenchus pseudorobustus (Steiner, 1914) Golden, 1956 (Tylenchida: Hoplolaimidae)

in Nematology
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Summary

Helicotylenchus microlobus is considered to be a junior synonym of H. pseudorobustus by several authors while others consider it as valid. To clarify the status of both species, 39 samples collected from various countries were subjected to statistical analyses that showed they could be grouped into six groups. Topotypes of H. pseudorobustus and H. microlobus belong to two different groups. However, samples in the other groups were morphologically intermediate between these two groups. Characters used in the past to uphold the validity of H. microlobus were variable and overlapping from group to group. The 28 samples studied are identified as H. pseudorobustus. Helicotylenchus microlobus, H. bradys and H. phalerus are confirmed as junior synonyms of H. pseudorobustus. There was no complete congruence between the morphological groups and molecular groups proposed by other authors. For these, two MOTU (Molecular Operational Taxonomic Unit) are accepted within H. pseudorobustus.

On the morphometric identity of populations of Helicotylenchus pseudorobustus (Steiner, 1914) Golden, 1956 (Tylenchida: Hoplolaimidae)

in Nematology

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References

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Figures

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    List of Helicotylenchus samples and species used in the present study.

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    (Continued.)

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    Multivariate analysis of 24 populations from Fortuner et al. (1984) using seven characters.

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    Hierarchical classification of 39 populations from Fortuner et al. (1984) and Subbotin et al. (2015) (see Table 1) based on a multivariate analysis using 17 characters.

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    Proportion of variance explained by the clustering presented in Figure 2 for each character (R2).

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    Morphological description of seven samples in group Pseudo-1, with the range of the population mean for each character (range = confidence interval centered on sample mean).

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    Morphological description of five samples in group Pseudo-2, with the range of the population mean for each character (range = confidence interval centered on sample mean).

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    Morphological description of five samples in group Intermediate-1, with the range of the population mean for each character (range = confidence interval centered on sample mean).

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    Morphological description of six samples in group Intermediate-2, with the range of the population mean for each character (range = confidence interval centered on sample mean).

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    Morphological description of five samples in group Micro, with the range of the population mean for each character (range = confidence interval centered on sample mean).

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    Confidence interval of the mean of anal body diam. A: Twenty-eight populations in five morphological groups; B: Eleven populations in two molecular groups. y-axis: population codes and groups; x-axis: anal body diam. in μm.

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    Confidence interval of the mean of position of phasmids. A: Twenty-eight populations in five morphological groups; B: Eleven populations in two molecular groups. y-axis: population codes and groups; x-axis: number of annuli between anus and phasmid levels.

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    Confidence interval of the mean of position of dorsal gland opening. A: Twenty-eight populations in five morphological groups; B: Eleven populations in two molecular groups. y-axis: population codes and groups; x-axis: distance between stylet base and dorsal gland opening in μm.

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    Fusion of inner incisures in the left and right sides of a topotype specimen of H. pseudorobustus. Reproduction of a 1984 pencil drawing in the archives of the senior author.

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