Interspecific Genetic Distances Research Articles

Identification and analysis of Corydalis boweri,Meconopsis horridula and their close related species of the same genus by using ITS2 DNA barcode

The study is aimed to ensure the quality and safety of medicinal plants by using ITS2 DNA barcode technology to identify Corydalis boweri, Meconopsis horridula and their close related species. The DNA of 13 herb samples including C. boweri and M. horridula from Lhasa of Tibet was extracted, ITS PCR were amplified and sequenced. Both assembled and web downloaded 71 ITS2 sequences were removed of 5. 8S and 28S. Multiple sequence alignment was completed and the intraspecific and interspecific genetic distances were calculated by MEGA 5.0, while the neighbor-joining phylogenetic trees were constructed. We also predicted the ITS2 secondary structure of C. boweri, M. horridula and their close related species. The results showed that ITS2 as DNA barcode was able to identify C. boweri, M. horridula as well as well as their close related species effectively. The established based on ITS2 barcode method provides the regular and safe detection technology for identification of C. boweri, M. horridula and their close related species, adulterants and counterfeits, in order to ensure their quality control, safe medication, reasonable development and utilization.

Identification of ungulates used in a traditional Chinese medicine with DNA barcoding technology.

Horns of Saiga antelope (Saiga tatarica) have always been an ingredient of “Lingyangjiao”, a traditional Chinese medicine (TCM). Persistent hunting for Saiga antelope has already threatened the survival of critical endangered populations in wild. To control the growing pressure, CITES and Chinese government have legislated for monitoring the trade of Saiga horns. However, similar ungulate horns are difficult to identify by their morphological characteristics, which has impeded the law enforcement. Besides Saiga antelope, other seven ungulate species which have similar horns are also sold and marked as “Lingyangjiao” in TCM markets to offset shortage of Saiga antelope horns. Such species are Gazella subgutturosa, Pantholops hodgsonii, Procapra picticaudata, Procapra gutturosa, Procapra przewalskii, Capra hircus, and Ovis aries. Our study aimed at implementing DNA barcoding technology to diagnose Saiga horns and the substitutes. We successfully extracted genomic DNA from horn samples. We recovered COI sequences of 644 bp with specific primers and 349 bp with nested PCR primers designed for degraded horn samples. The mean interspecific genetic distance of data set of the 644-bp full barcodes and the 349-bp mini-barcodes was 14.96% and 15.38%, respectively, and the mean intraspecific distance was 0.24% and 0.20%, respectively. Each species formed independent clades in neighbor-joining (NJ) phylogenetic tree of the two data sets with >99% supporting values, except P. gutturosa and P. przewalskii. The deep genetic distances gap and clear species clades in NJ tree of either full barcodes or mini-barcodes suggest that barcoding technology is an effective tool to diagnose Saiga horns and their substitutes. Barcoding diagnosis protocol developed here will simplify diagnosis of “Lingyangjiao” species and will facilitate conservation of endangered ungulates involved in TCM “Lingyangjiao” markets, especially the Saiga antelope.

DNA-Based Identification of Lepidoptera Associated with Citrus in South Africa

A number of insects, primarily Lepidoptera, cause damage to citrus in South Africa. A major limitation to the management and control of these pests is their correct identification. The aim of this study was to develop a database of gene sequences to aid in the identification of these Lepidoptera. Multiple specimens of 12 species were sequenced for the ~650 bp of the cytochrome oxidase I gene. These sequence data were supplemented and validated using sequences available in public databases. Results showed that each species could be unambiguously identified, and neighbour-joining analysis based on K2P distances formed highly supported, distinct clusters for each species, i.e. the maximum intraspecific genetic distance was less than that of the minimum interspecific genetic distances. Thus, this data set provides a molecular means to successfully identify the most important Lepidoptera associated with citrus in South Africa.

Molecular phylogeny and diagnosis of species of the family Protostrongylidae from caprine hosts in Uzbekistan.

Protostrongylids are important pulmonary parasites of ungulates, particularly caprines. Their complex life cycles involve terrestrian gastropods as intermediate hosts. Morphological discrimination of larvae in feces and snails is impossible to the species level, and molecular data are missing for many species. To improve diagnosis and epidemiology of protostrongylids, this study describes internal transcribed spacer 2 (ITS-2) sequences for five protostrongylid and one metastrongylid species from Uzbekistan. Morphological and molecular analyses identified Protostrongylus rufescens, Protostrongylus hobmaieri, Protostrongylus sp., Spiculocaulus leuckarti, and Cystocaulus ocreatus. Sequence differences between ITS-2 were sufficient to allow species identification, e.g., in the Protostrongylinae intraspecific and interspecific genetic distances ranged between 0-0.01 and 0.05 and 0.16, respectively. There was one exception in the Elaphostrongylidae with identical ITS-2 sequences in Elaphostrongylus cervi and Elaphostrongylus rangiferi questioning their status as valid species. Maximum likelihood analysis sequences largely supported the currently assumed phylogenetic relationships among Protostrongylidae as predicted using morphological characters. The monophyly of the subfamilies Varestrongylinae, Elaphostrongylinae, and Protostrongylinae was corroborated with support values in Shimodaira-Hasegawa or Bayesian modifications of the approximate likelihood ratio test (aLRT) ≥97%, but support for Muellerinae was weak (8 and 52%, respectively) since Muellerius capillaris differs significantly from the other Muellerinae. On the genus level, paraphyly of the genus Protostrongylus was confirmed since the members of the genera Spiculocaulus and Orthostrongylus were located within the Protostrongylus cluster (aLRT ≥99%). Maximum likelihood unequivocally assigned every unique sequence to the correct species confirming suitability of ITS-2 regions for diagnosis protostrongylids except of E. cervi and E. rangiferi.

DNA Barcoding Analysis of Commercial Freshwater Fish Species Cultured in China

In this study, thirteen commercial freshwater fish species cultured in China, and one hybrid F1 (Megalobrama amblycephala ♀ × Erythroculter ilishaeformis ♂), were barcoded for a 860 bp region of the mitochondrial cytochrome oxidase subunit I (COI) gene. The results showed that a neighbor-joining (NJ) tree was constructed based on COI sequence clustered species in accordance with their taxonomic classification. Hybrid F1 could not be differentiated from M.amblycephalaj in the neighbor-joining (NJ) tree. There was a significant negative correlation between interspecific hybrid compatibility and genetic distance (R2 = 0.96). Hybrid compatibility can be predicted by the interspecific genetic distance.

Molecular identification of the genus Thryssa based on DNA barcoding.

DNA barcoding is an effective method for identifying species by analyzing one or a few short standardized DNA sequences. In this study, we examined the utility of mitochondrial cytochrome oxidase subunit I (COI) sequences as a DNA barcode for the identification of six species belonging to the genus Thryssa: T. dussumieri, T. hamiltonii, T. kammalensis, T. mystax, T. setirostris, and T. vitrirostris. We obtained an intraspecific distance of 0.000 for T. vitrirostris and T. hamiltonii, 0.006 for T. mystax, 0.002 for T. dussumieri, and 0.005 for T. kammalensis. The average intraspecific distance was 0.002, while the average interspecific distance was 0.137. Thus, the interspecific genetic distance was approximately 67-fold larger than the intraspecific genetic distance; the average genetic distance among species was greater than the minimum of 0.020 between species suggested elsewhere. The genetic distance between T. vitrirostris and T. mystax was 0.003. A maximum-likelihood phylogenetic tree constructed using best-fitting tree topology showed distinct clusters corresponding to the species (except for T. vitrirostris and T. mystax). The closest relationship was found between T. vitrirostris and T. mystax. These two species clustered together in the phylogenetic tree. This conclusion contradicts the evolutionary relationship based on morphological classification.

DNA barcoding and phylogenetic relationships of genera Picoides and Dendrocopos (Aves: Picidae).

Picoides and Dendrocopos are two closely related genera of woodpeckers (family Picidae), and members of these genera have long been the subjects of phylogenetic debate. Mitochondrial cytochrome c oxidase subunit I (COI) is a powerful marker for the identification and phylogenetic study of animal species. In the present study, we analyzed the COI barcodes of 21 species from the two genera, and 222 variable sites were identified. Kimura two-parameter distances were calculated between barcodes. The average interspecific genetic distance was more than 20 times higher than the average intraspecific genetic distance. The neighbor-joining method was used to construct a phylogenetic tree, and all of the species could be discriminated by their distinct clades. Picoides arcticus was the first to split from the lineage, and the other species were grouped into two divergent clades. The results of this study indicated that the COI genetic data did not support the monophyly of Picoides and Dendrocopos.

Análise de distância genética entre acessos do gênero Psidium via marcadores ISSR

O objetivo deste trabalho foi avaliar a distância genética entre 37 acessos da espécie cultivada Psidium guajava, L. (goiaba) e de araçás do gênero Psidium do banco de germoplasma da Universidade Estadual do Norte Fluminense (UENF), via marcadores moleculares ISSR. Nos 17 marcadores selecionados, foram obtidas 216 bandas polimórficas. Pelo método de agrupamento UPGMA, houve a formação de cinco principais grupos. Os acessos de araçá da espécie P. cattleyanum Sabine , ficaram alocados nos grupos I e II. No grupo II, foi observada, dentro da espécie P cattleyanum, maior proximidade com a goiabeira. No grupo III, ficou alocado o acesso da espécie P. guineense Sw (araçá-do-campo) e dentre os araçás, foi o que ficou mais próximo da goiaba. Os genótipos de goiabeira ficaram alocados do grupo IV e V, confirmando sua alta divergência. Os marcadores moleculares foram eficientes em estimar a distância genética intra e interespecífica.

Identification of Peucedani Radix, Peucedani Decursivi Radix and its adulterants using ITS2 sequence

In order to identify Peucedani Radix, Peucedani Decursivi Radix and their adulterants, the internal transcribed spacer 2 (ITS2) regions of Peucedani Radix, Peucedani Decursivi Radix and their adulterants were amplified and bidirectionally sequenced based on the Principles for Molecular Identification of Traditional Chinese Materia Medica Using DNA Barcoding, which has been promulgated by Chinese Pharmacopoeia Commission. Sequences were analyzed and assembled by Codon Code Aligner V3. 7.1. The relevant data were analyzed by MEGA 5. 0. Species identification analyses were performed by using the nearest distance methods and neighbor-joining (NJ) methods. The result showed that the ITS2 sequence lengths of Peucedani Radix were 229-230 bp and the average intra-specific genetic distances were 0.005. The ITS2 sequence lengths of Peucedani Decursivi Radix were 227 bp and the sequences contained no variation site. The average inter-specific K2P genetic distance of Peucedani Radix, Peucedani Decursivi Radix and their adulterants species were 0.044 and 0.065 respectively. The minimum inter-specific divergence is larger than the maximum intra-specific divergence of Peucedani Decursivi Radix. The nearest distance methods and NJ trees results indicated that Peucedani Radix, Peucedani Decursivi Radix and their adulterants species could be identification clearly. The ITS2 regions can stably and accurately distinguish Peucedani Radix, Peucedani Decursivi Radix and their adulterants.

Molecular diversity of Germany's freshwater fishes and lampreys assessed by DNA barcoding.

This study represents the first comprehensive molecular assessment of freshwater fishes and lampreys from Germany. We analysed COI sequences for almost 80% of the species mentioned in the current German Red List. In total, 1056 DNA barcodes belonging to 92 species from all major drainages were used to (i) build a reliable DNA barcode reference library, (ii) test for phylogeographic patterns, (iii) check for the presence of barcode gaps between species and (iv) evaluate the performance of the barcode index number (BIN) system, available on the Barcode of Life Data Systems. For over 78% of all analysed species, DNA barcodes are a reliable means for identification, indicated by the presence of barcode gaps. An overlap between intra- and interspecific genetic distances was present in 19 species, six of which belong to the genus Coregonus. The Neighbour-Joining phenogram showed 60 nonoverlapping species clusters and three singleton species, which were related to 63 separate BIN numbers. Furthermore, Barbatula barbatula, Leucaspius delineatus, Phoxinus phoxinus and Squalius cephalus exhibited remarkable levels of cryptic diversity. In contrast, 11 clusters showed haplotype sharing, or low levels of divergence between species, hindering reliable identification. The analysis of our barcode library together with public data resulted in 89 BINs, of which 56% showed taxonomic conflicts. Most of these conflicts were caused by the use of synonymies, inadequate taxonomy or misidentifications. Moreover, our study increased the number of potential alien species in Germany from 14 to 21 and is therefore a valuable groundwork for further faunistic investigations.

DNA barcodes for discriminating the medicinal plant Isatis indigotica Fort. (Cruciferae) and its adulterants

Isatis indigotica Fort. (Cruciferae) is a biennial medicinal plant. In order to protect the decreasing natural genetic resources of I. indigotica, three candidate DNA barcodes (ITS2, trnL-F and rbcL) were employed to establish an accurate and effective identification system for I. indigotica. The results demonstrated that all three candidate DNA barcodes have performed very well in I. indigotica. The interspecific genetic distances were obviously greater than the intraspecific distance among I. indigotica as indicated by ITS2, trnL-F and rbcL. Sequence alignment analysis of I. indigotica genotypes revealed that four SNPs (54, 108, 146 and 181 bp) located in ITS2, three (2, 30, 709 bp) in trnL-F and one (531 bp) in rbcL, respectively. UPGMA phylogenetic tree constructed from trnL-F and rbcL could allote I. indigotica to the correct corresponding genus, whereas rbcL could not distinguish I. indigotica from its adulterants. Meanwhile, UPGMA tree of ITS2 could accurately identify I. indigotica from its adulterants according to the corresponding species. Consequently, it can be concluded that ITS2 is a more suitable and accurate DNA barcode for identifying I. Indigotica and its adulterants than trnL-F and rbcL.

Testing DNA barcodes in closely related species of Curcuma (Zingiberaceae) from Myanmar and China.

The genus Curcuma L. is commonly used as spices, medicines, dyes and ornamentals. Owing to its economic significance and lack of clear-cut morphological differences between species, this genus is an ideal case for developing DNA barcodes. In this study, four chloroplast DNA regions (matK, rbcL, trnH-psbA and trnL-F) and one nuclear region (ITS2) were generated for 44 Curcuma species and five species from closely related genera, represented by 96 samples. PCR amplification success rate, intra- and inter-specific genetic distance variation and the correct identification percentage were taken into account to assess candidate barcode regions. PCR and sequence success rate were high in matK (89.7%), rbcL (100%), trnH-psbA (100%), trnL-F (95.7%) and ITS2 (82.6%) regions. The results further showed that four candidate chloroplast barcoding regions (matK, rbcL, trnH-psbA and trnL-F) yield no barcode gaps, indicating that the genus Curcuma represents a challenging group for DNA barcoding. The ITS2 region presented large interspecific variation and provided the highest correct identification rates (46.7%) based on BLASTClust method among the five regions. However, the ITS2 only provided 7.9% based on NJ tree method. An increase in discriminatory power needs the development of more variable markers.

Morphological and genetic characteristics of the anisakid nematode Raphidascaris acus from the southwest Caspian Sea: evidence for the existence of sibling species within a species complex.

Recently, it has been shown that many nematode species are in fact species complex, using exact morphological and genetic studies. In this case, there are no such studies related to the genus Raphidascaris Railliet & Henry, 1915. Herein, the morphological and genetic variations among the Iranian population of the species Raphidascaris acus (Bloch, 1779) Railliet & Henry, 1915 and the other allopatric populations with morphological and genetic information were compared to show whether this species can be considered as a species complex. R. acus is an anisakid species and has been frequently reported from different host species from the Caspian Sea. Nonetheless, there are no morphological and genetic information for this species from the region. In the present study, a total of 20 specimens of R. acus were collected from Esox lucius Linnaeus, and the morphology of the Caspian population of this species was surveyed for the first time using both light and scanning electron microscopy. Meanwhile, some parts of ribosomal DNA (rDNA) including internal transcribed spacer 1 (ITS1), 5.8 s, and ITS2 were sequenced and presented as the genetic marker for this species. To understand whether R. acus can be considered as a species complex, the Caspian population of this species was compared morphologically with the allopatric populations of Czech and Canada and genetically with the allopatric population of Poland (Vistula lagoon). Morphologically, there was no difference between the Caspian and Czech populations, but the Caspian and Canadian populations differed in the length of ejaculatory duct and the presence of small triangular elevation between the bases of subventral lips. The nucleotide difference between the Caspian and Polish populations was 4.48%. In comparison with the interspecific genetic distances in the genus Raphidascaris, this value is notable. In conclusion, based on morphological and genetic differences among the allopatric populations of R. acus, this species is probably a species complex. Nonetheless, the definitive taxonomic decision in recognizing R. acus as a species complex and the description of its sibling species depend on surveying other allopatric populations morphologically and genetically accompanied by an evaluation of reproductive isolation among them.

Genetic Variation of Rice Populations Estimated Using nrDNA ITS Region Sequence

The rice belonging to Oryza sativa is not only has significant economic importance, for it is the major source of nutrition for about 3 billion all around the world. But also plays a vital role as a model organism, because it has a number of advantages to be a model plant, such as efficient transformation system and small genome size. Many methods and techniques have been conducted to attempt to distinguish different Oryza sativa species, such as amplified fragment length polymorphism (AFLP), random amplified polymorphic DNA (RAPD), simple sequence repeat (SSR) and so on. However, studies using sequence analysis of internal transcribed spacer (ITS), a region of ribosomal RNA has not been reported until now. This study was undertaken with an aim to understand the phylogenetic relationships among sixteen isolates of Oryza sativa collected from abroad and fifteen isolates collected from Korea, using ribosomal RNA (rRNA) internal transcribed spacer (ITS) sequences to compare the phylogeny relationships among different Oryza sativa species. The size variation obtained among sequenced nuclear ribosomal DNA (nrDNA) ITS region ranged from 515bp to 1000bp. The highest interspecific genetic distance (GD) was found between Sfejare 45 (FR12) and Anapuruna (FR15). Taebong isolate showed the least dissimilarity of the ITS region sequence with other thirty isolates. This consequence will help us further understanding molecular diversification in intra-species population and their phylogenetic analysis.

Developing a new molecular marker for aphid species identification: Evaluation of eleven candidate genes with species-level sampling

The mitochondrial cytochrome c oxidase subunit I (COI) gene has been utilized as a molecular marker for aphid species identification. However, this gene has sometimes resulted in misidentification because of low interspecific genetic divergences between some species pairs. In this study, to propose new molecular markers for the family Aphididae, we first screened 2289 sequences of 11 genes (COI, COII, CytB, ATP6, lrRNA, srRNA, ITS1, ITS2, EF1a, 18S, and 28S) collected from the GenBank. Among the 11 genes, ATP6 gene revealed the largest genetic divergence among congeneric species with the smallest divergence among conspecific individuals; in contrast, species pairs with low genetic divergences (<1%) were not observed. Secondly, for statistically testing the usefulness of ATP6 gene in species identification, we analyzed genetic distances between all of the combinations of 32 individuals of 20 species for both COI and ATP6 genes. The ATP6 gene showed lower intraspecific (on average 0.08%) and higher interspecific (on average 8.28%) genetic distances than the COI gene (on average 0.19% and 6.24%, respectively) for the same pairs of individuals. This study corroborates the usefulness of the ATP6 gene as a new molecular marker that could improve the misidentification problems that are inherent with the COI gene.

Identification of Albiziae Cortex, Albiziae Flos and their adulterants using ITS2 barcoding

The ITS2 barcode was used to accurately identify Albiziae Cortex, Albiziae Flos and their adulterants in this study. A total of46 samples from Albiziae Cortex, Albiziae Flos and their adulterants were collected. The ITS2 regions were amplified and sequenced. Sequences were assembled using the CodonCode Aligner. The genetic distances of ITS2 region were calculated using MEGA 5.0. BLAST1, nearest distance and phylogenetic tree (NJ-tree) methods were used to assess the identification efficiency of the ITS2 barcode. The results revealed that the intraspecific genetic distances of Albizia julibrissin were lower than the interspecific genetic distances between A. julibrissin and its adulterants. The identification efficiency of ITS2 barcode using BLAST1 was 100%. The NJ-tree showed that A. julibrissin and their adulterants can be easily differentiated according to their monophyly. The ITS2 barcode is suitable to be as a barcode to identify Albiziae Cortex, Albiziae Flos and their adulterants.

Identification of Cimicifugae Rhizoma and its adulterants using ITS2 sequence

In order to identify Cimicifugae Rhizoma from its adulterants and to ensure its safe use, the internal transcribed spacer 2 (ITS2) sequence of Cimicifugae Rhizoma and its adulterants were amplified and bidirectionally sequenced by DNA barcoding technology. Sequence assembly and consensus sequence generation were performed by the CodonCode Aligner V3.7.1. The genetic distances were computed by MEGA 5.0. Identification analyses were performed using neighbor-joining (NJ) methods. The length of ITS2 sequence of the three origin plants of Cimicifugae Rhizoma include Cimicifuga heracleifolia, C. foetida, C. dahurica was 217, 219 and 219 bp, respectively. Their intraspecific genetic distance was much lower than the interspecific genetic distance with their closely related species. The NJ tree of ITS2 indicated that the three origin plants of Cimicifugae Rhizoma formed a monophyletic clade, Cimicifugae Rhizoma and its adulterants could be distinguished clearly. The authors proposed that ITS2 sequence was suitable for the authentication of Cimicifugae Rhizoma and its adulterants.

Identification of Pyrrosiae Folium and its adulterants based on psbA-trnH sequence

In this study, the psbA-trnH sequence as DNA barcode was used to evaluate the accuracy and stability for identification pteridophyte medicinal material Pyrrosiae Foliumas from adulterants. Genomic DNA from 106 samples were extracted successfully. The Kimura 2-Parameter (K2P) distances and ML tree were calculated using software MEGA 6.0. The intra-specific genetic distances of 3 original plants were lower than inter-specific genetic distances of adulterants. The ML tree indicated that Pyrrosiae Folium can be distinguished from its adulterants obviously. Therefore, the psbA-trnH sequence as a barcode of the pteridophyte, can accurately and stably distinguish Pyrrosiae Folium from its adulterants.

Identification of Atractylodis Macrocephalae Rhizoma and Atractylodis Rhizoma from their adulterants using DNA barcoding

Atractylodis Macrocephalae Rhizoma and Atractylodis Rhizoma were widely used in strengthening spleen under different disease conditions, and were easily and often misused each other. Therefore, DNA barcode was used to distinguish Atractylodis Macrocephalae Rhizoma and Atractylodis Rhizoma from their adulterants to ensure the safe use. The sequence lengths of ITS2 of Atractylodes macrocephala, Atractylodis Rhizoma (A. lancea, A. japonica and A. coreana) were both 229 bp. Among the ITS2 sequences of A. macrocephala, only one G/C transversion was detected at site 98, and the average GC content was 69.42%. No variable site was detected in the ITS2 sequences of A. lancea. The maximum K2P intraspecific genetic distances of both A. japonica and A. coreana were 0.013. The maximum K2P intraspecific genetic distances of A. macrocephala, A. lancea, A. japonica and A. coreana were less than the minimum interspecific genetic distance of adulterants. The ITS2 sequences in each of these polytypic species were separated into pairs of divergent clusters in the NJ tree. DNA barcoding could be used as a fast and accurate identification method to distinguish Atractylodis Macrocephalae Rhizoma, Atractylodis Rhizoma, from their adulterants to ensure its safe use.

Identification of Bupleurum chinense and B. longiradiatum based on ITS2 barcode

In this study, ITS2 barcode was used to identify Bupleurum chinense and B. longiradiatum. The ITS2 regions of 48 samples were amplified and sequenced. The sequences obtained above were aligned and the K2P distances were calculated. We used three methods, BLAST1, nearest distance and phylogenetic tree (NJ-tree), to test the identification ability. The results showed that the maximum intraspecific genetic distance of B. chinense was 0.013, and the minimum interspecific genetic distance between B. chinense and B. longiradiatum was 0.049. The NJ-tree can easily identify B. chinense and B. longiradiatum. Therefore, the ITS2 barcode is suitable to identify B. chinense and B. longiradiatum.