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

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

Class of marker	Genetic marker	Nematodes^a		Trematodes^a		Cestodes^a
Class of marker	Genetic marker	Mean ± SD [95 CI%]	Closely related species^b	Mean ± SD [95 CI%]	Closely related species^b	Mean ± SD [95 CI%]	Closely related species^b
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
Nuclear rRNA	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
Nuclear spacer	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
Mt rRNA	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

*Statistically significant difference of mean genetic distances between the markers at P < 0.000001, according to Kruskal–Wallis test with Dunn’s posthoc analysis
^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
^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

ISSN: 1756-3305