Ratios and Indexes in Nematode Taxonomy

Fortuner, Renaud

doi:10.1163/002925990x00176

Cited by 11 publications

(9 citation statements)

References 2 publications

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“…Concerning to other plant-parasitic nematodes, Fortuner (1984) noted that the indices a, c, and c' are often useful to accurately identify species of Helicot ylenchus (Steiner, 1945). Fortuner (1990) also revealed that the features related to body size (length and indices of a and b) showed a high correlation to each oth-er for Hirschmanniella belli. Subbotin et al (1999) also stated that morphometric character analysis is suitable for separating populations within the H. avenae group.…”

Section: Discussionmentioning

confidence: 73%

New data on known species of Hirschmanniella and Pratylenchus (Rhabditida, Pratylenchidae) from Iran and South Africa

Shokoohi

Abolafia

Mashela

et al. 2019

Journal of Nematology

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Hirschmanniella anchoryzae from Iran and Pratylenchus hippeastri from South Africa were recovered during a survey of plant-parasitic nematodes belonging to the family Pratylenchidae. Both species were studied using morphological and molecular techniques. Hirschmanniella anchoryzae is identified based on the flattened head, short stylet (19-22 µm), excretory pore position (anterior to pharyngo-intestinal junction), spicule length (27-30 µm), and existence of an axial mucro at the tail end. Phylogenetic analysis using 28S rDNA showed monophyly of Hirschmanniella which Iranian H. anchoryzae placed close to H. halophila (EU620464; EU620465). This result was supported by the principal component analysis of Hirschmanniella species. SEM observation of the South African population of P. hip peastri showed the presence of two annuli in the lip region. Morphometric characters resembled those of specimens earlier reported from South Africa. Hierarchal cluster using morphometrical criteria showed that the Floridian (USA) and South African populations form a group. However, the principal component analysis showed variation within this species. The molecular study of P. hippeastri populations using 18S, ITS, 28S rDNA, and COI of mtDNA showed that all P. hippeastri cluster in one group and confirmed the identification of the species using both morphological and molecular techniques. In addition, the results indicated that South African populations group close to the USA populations. Illustrations of both species including light and scanning electron microscopy observations for P. hippeastri are provided.

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Section: Discussionmentioning

confidence: 73%

New data on known species of Hirschmanniella and Pratylenchus (Rhabditida, Pratylenchidae) from Iran and South Africa

Shokoohi

Abolafia

Mashela

et al. 2019

Journal of Nematology

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“…Expressing tail length as a ratio of body diameter at the anus is uncertain because the level at the anterior lip is often different from that at the posterior lip, both of which are exible and may protrude in mounted specimens. De Man's ratios are frequently used for summarising measurements despite the fact that theoretical and practical observations show that these ratios are not, as was originally intended, independent of body length (Fortuner, 1990).…”

Section: Discussionmentioning

confidence: 99%

The taxonomy of the family Xyalidae Chitwood, 1951 (Monhysterida: Nematoda): a cladistic analysis

Nicholas¹,

Trueman²

2002

Nematol

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A cladistic analysis of the family Xyalidae has been carried out, with selected Monhysteridae and Sphaerolaimidae as presumptive outgroups. Forty nine characters, taken from published descriptions, were scored for 91 species from 33 genera. The way in which the characters were coded is illustrated by drawings and graphs. Phylogenetic analyses were conducted with the programs PAUP*4.0d65 and PAUP*4.0b2. Neighbour-joining and parsimony trees were constructed and the preferred consensus parsimony tree is presented. The tree has been divided into 15 groups for purposes of discussion. All eight species of Monhysteridae form a separate clade consistent with outgroup status, but the four species of Sphaerolaimidae are not separated from Xyalidae. Several of the Daptonema species, Pseudosteineria plus Steineria, and Rhynchonematinae form three well supported clades. Other groupings are much less well supported and are presumed to be paraphyletic. Many published descriptions do not include suf cient detail to allow relationships to be determined and suggestions are made as to data which should be included in future taxonomic descriptions of Xyalidae.

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“…Note that indices and quantitative data can be combined in a discriminant function analysis when they are not highly correlated (Fortuner, 1990).…”

Section: Discussionmentioning

confidence: 99%

Experimental induction of intraspecific morphometric variability in a single population of Halicephalobus cf. gingivalis may surpass total interspecific variability

Fonderie

Steel

Moens

et al. 2013

Nematol

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Although molecular techniques are revolutionising nematode taxonomy, morphological data still form the basis of nematode species descriptions. However, morphological characters show a natural variability that should be taken into account before describing new species. The current study presents the results of an elaborate morphometric study of Halicephalobus cf. gingivalis, including 15 measurements and 13 indices of 540 specimens, the progeny of a single parthenogenetic female and cultured under different temperature and food conditions and measured in different adult age groups, i.e., young adults with a developed vulva but before the onset of oviposition, aduhs laying eggs, and old, post-reproductive adults near the end of their life cycle. The morphometric characters were analysed using both univariate (analysis of variance) and multivariate (principal components and canonical discriminant analysis) techniques. The main results reveal that the morphometric characters most used in Halicephalobus identification keys have a huge variability within a single progeny, e.g., body length 1.9 times longer than the shortest or ratio VA/tail length 3.9 times larger than the smallest. This variability has a magnitude that has not been observed in nematodes before. Further, by changing the environmental factors, the morphometric characters are influenced to an extent that one could assign -with seemingly 'statistical support' -different 'species' of the genus to different subpopulations. With this experimental study we provide convincing elements to advocate an integrative taxonomic approach and to discourage the description of new species based only on morphometric differences.

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Ratios and Indexes in Nematode Taxonomy

Cited by 11 publications

References 2 publications

New data on known species of Hirschmanniella and Pratylenchus (Rhabditida, Pratylenchidae) from Iran and South Africa

New data on known species of Hirschmanniella and Pratylenchus (Rhabditida, Pratylenchidae) from Iran and South Africa

The taxonomy of the family Xyalidae Chitwood, 1951 (Monhysterida: Nematoda): a cladistic analysis

Experimental induction of intraspecific morphometric variability in a single population of Halicephalobus cf. gingivalis may surpass total interspecific variability

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