DNA Barcoding of Birds at a Migratory Hotspot in Eastern Turkey Highlights Continental Phylogeographic Relationships

Mitochondrial DNA barcoding of mosquito species (Diptera: Culicidae) in Thailand

The correct identification of mosquito species is important for effective mosquito vector control. However, the standard morphological identification of mosquito species based on the available keys is not easy with specimens in the field due to missing or damaged morphological features during mosquito collections, often leading to the misidentification of morphologically indistinguishable. To resolve this problem, we collected mosquito species across Thailand to gather genetic information, and evaluated the DNA barcoding efficacy for mosquito species identification in Thailand. A total of 310 mosquito samples, representing 73 mosquito species, were amplified using mitochondrial cytochrome c oxidase subunit I (COI) primers. The average maximum intraspecific genetic variation of the 73 mosquito species was 1% ranged from 0–5.7%. While, average minimum interspecific genetic variation (the distance to the nearest neighbour) of the 73 mosquito species was 7% ranged from 0.3–12.9%. The identification of success rates based on the “Best Match,” “Best Close Match,” and “All Species Barcodes” methods were 97.7%, 91.6%, and 81%, respectively. Phylogenetic analyses of Anopheles COI sequences demonstrated a clear separation between almost all species (except for those between An. baimaii and An. dirus), with high bootstrap support values (97%–99%). Furthermore, phylogenetic analyses revealed potential sibling species of An. annularis, An. tessellatus, and An. subpictus in Thailand. Our results indicated that DNA barcoding is an effective molecular approach for the accurate identification of mosquitoes in Thailand.

Molecular identification of Todiramphus chloris subspecies on the Arabian Peninsula using three mitochondrial barcoding genes and ISSR markers

The Collared Kingfisher (Todiramphus chloris) is widely distributed across the Indian and western Pacific Oceans and consists of about 50 subspecies. Two different subspecies of T. chloris occur in the Arabian Peninsula: T. c. abyssinicus from the Red Sea coast and T. c. kalbaensis from the Arabian Sea coast in the United Arab Emirates and Oman. The aim of this study was to determine the molecular relationship between the two Arabian subspecies and to establish the first DNA barcodes from the Arabian Peninsula for this species. Three different mitochondrial genes were used: (i) cytochrome c oxidase subunit I (COI), (ii) 12S rRNA (12S) and (iii) NADH dehydrogenase-1 (ND1). The COI gene sequences of the two subspecies were 100% identical, while the 12S and ND1 gene sequences revealed a unique single nucleotide variation between the two subspecies. Thus, this single nucleotide variation can be used as a DNA barcode to discriminate between two subspecies. Furthermore, the genetic profile or fingerprint for both subspecies were compared using ten primers of the highly polymorphic nuclear markers (Inter Simple Sequence Repeat, ISSR). As expected, the DNA analysis of the ISSR markers was able to distinguish between the specimens of the two subspecies. These results suggest that T. c. abyssinicus and T. c. kalbaensis are not identical and thus belong to different subspecies. Besides, the sequences of the COI gene for T. c. abyssinicus and T. c. kalbaensis differs by only 1.28% from T. sanctus suggesting that the Arabian subspecies are closely related to the Sacred Kingfisher (T. sanctus).

Categorization of species as native or nonnative using DNA sequence signatures without a complete reference library

New genetic diagnostic approaches have greatly aided efforts to document global biodiversity and improve biosecurity. This is especially true for organismal groups in which species diversity has been underestimated historically due to difficulties associated with sampling, the lack of clear morphological characteristics, and/or limited availability of taxonomic expertise. Among these methods, DNA sequence barcoding (also known as "DNA barcoding") and by extension, meta-barcoding for biological communities, has emerged as one of the most frequently utilized methods for DNA-based species identifications. Unfortunately, the use of DNA barcoding is limited by the availability of complete reference libraries (i.e., a collection of DNA sequences from morphologically identified species), and by the fact that the vast majority of species do not have sequences present in reference databases. Such conditions are critical especially in tropical locations that are simultaneously biodiversity rich and suffer from a lack of exploration and DNA characterization by trained taxonomic specialists. To facilitate efforts to document biodiversity in regions lacking complete reference libraries, we developed a novel statistical approach that categorizes unidentified species as being either likely native or likely nonnative based solely on measures of nucleotide diversity. We demonstrate the utility of this approach by categorizing a large sample of specimens of terrestrial insects and spiders (collected as part of the Moorea BioCode project) using a generalized linear mixed model (GLMM). Using a training data set of known endemic (n = 45) and known introduced species (n = 102), we then estimated the likely native/nonnative status for 4,663 specimens representing an estimated 1,288 species (412 identified species), including both those specimens that were either unidentified or whose endemic/introduced status was uncertain. Using this approach, we were able to increase the number of categorized specimens by a factor of 4.4 (from 794 to 3,497), and the number of categorized species by a factor of 4.8 from (147 to 707) at a rate much greater than chance (77.6% accuracy). The study identifies phylogenetic signatures of both native and nonnative species and suggests several practical applications for this approach including monitoring biodiversity and facilitating biosecurity.

DNA barcoding a unique avifauna: an important tool for evolution, systematics and conservation

BACKGROUND

DNA barcoding utilises a standardised region of the cytochrome c oxidase I (COI) gene to identify specimens to the species level. It has proven to be an effective tool for identification of avian samples. The unique island avifauna of New Zealand is taxonomically and evolutionarily distinct. We analysed COI sequence data in order to determine if DNA barcoding could accurately identify New Zealand birds.

RESULTS

We sequenced 928 specimens from 180 species. Additional Genbank sequences expanded the dataset to 1416 sequences from 211 of the estimated 236 New Zealand species. Furthermore, to improve the assessment of genetic variation in non-endemic species, and to assess the overall accuracy of our approach, sequences from 404 specimens collected outside of New Zealand were also included in our analyses. Of the 191 species represented by multiple sequences, 88.5% could be successfully identified by their DNA barcodes. This is likely a conservative estimate of the power of DNA barcoding in New Zealand, given our extensive geographic sampling. The majority of the 13 groups that could not be distinguished contain recently diverged taxa, indicating incomplete lineage sorting and in some cases hybridisation. In contrast, 16 species showed evidence of distinct intra-species lineages, some of these corresponding to recognised subspecies. For species identification purposes a character-based method was more successful than distance and phylogenetic tree-based methods.

CONCLUSIONS

DNA barcodes accurately identify most New Zealand bird species. However, low levels of COI sequence divergence in some recently diverged taxa limit the identification power of DNA barcoding. A small number of currently recognised species would benefit from further systematic investigations. The reference database and analysis presented will provide valuable insights into the evolution, systematics and conservation of New Zealand birds.