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Table 3 Properties of the different classes of genetic marker in terms of their quantitative suitability for distinguishing between species of helminths

From: Assessing the suitability of mitochondrial and nuclear DNA genetic markers for molecular systematics and species identification of helminths

Class of marker Genetic marker Nematodesa Trematodesa Cestodesa
Mean ± SD [95 CI%] Closely related speciesb Mean ± SD [95 CI%] Closely related speciesb Mean ± SD [95 CI%] Closely related speciesb
Nuclear rRNA 18S rRNA 0 0.001 0.004* ± 0.002 [0.002–0.005] 0.002 0.017* ± 0.006 [0.015–0.018] 0.003
28S rRNA 0.001 ± 0.001 [0–0.013] 0.002 0.024* ± 0.014 [0.020–0.027] 0.006 NA NA
Nuclear spacer ITS1 0.005 ± 0.011 [0–0.018] 0.025 0.045 ± 0.041 [0.023–0.067] 0 0.307 ± 0.283 [0.090–0.525] 0.659
ITS2 0.117 ± 0.166 [0–1.610] 0.235 0.031 ± 0.023 [0.019–0.043] 0 0.338* ± 0.124 [0.780–1.456] NA
Mt protein-coding COI 0.026 ± 0.035 [0–0.056] 0.094 0.158 ± 0.040 [0.136–0.179] 0.089 0.085 ± 0.023 [0.079–0.090] 0.046
COII 0.031 ± 0.043 [0–0.068] 0.091 0.193 ± 0.062 [0.160–0.226] 0.113 0.112 ± 0.030 [0.105–0.119] 0.029
cytB 0.036 ± 0.038 [0.004–0.068] 0.166 0.174 ± 0.044 [0.151–0.198] 0.080 0.109 ± 0.028 [0.103–0.116] 0.041
NAD1 0.032 ± 0.043 [0–0.068] 0.126 0.195 ± 0.058 [0.163–0.227] 0.083 0.132 ± 0.031 [0.125–0.140] 0.048
Mt rRNA 12S rRNA 0.015 ± 0.023 [0–0.035] 0.052 0.133 ± 0.045 [0.109–0.157] 0.079 0.081 ± 0.023 [0.769–0.087] 0.030
16S rRNA 0.021 ± 0.024 [0–0.041] 0.076 0.148 ± 0.050 [0.121–0.174] 0.080 0.080 ± 0.025 [0.074–0.086] 0.024
  1. *Statistically significant difference of mean genetic distances between the markers at P < 0.000001, according to Kruskal–Wallis test with Dunn’s posthoc analysis
  2. aGenetic distances among nematodes (Ascaris, Parascaris, Anisakis, Toxocara and Onchocerca), trematodes (Opisthorchis, Clonorchis, Echinostoma, Fasciola, Paragonimus and Dicrocoelium) and cestodes (Taenia, Echinococcus and Hymenolepis) were used to calculate mean interspecific genetic distances
  3. bClosely related species are those regarded as close sister species. If there are adequate interspecies differences between these, a marker is likely to be suitable for use in molecular identification at the species level. Examples used are Toxocara cati vs T. canis for nematodes, Fasciola hepatica vs F. gigantica for trematodes and Taenia saginata vs T. asiatica for cestodes