Part of a series on |
DNA barcoding |
---|
By taxa |
Other |
DNA barcoding in diet assessment is the use of DNA barcoding to analyse the diet of organisms. [1] [2] and further detect and describe their trophic interactions. [3] [4] This approach is based on the identification of consumed species by characterization of DNA present in dietary samples, [5] e.g. individual food remains, regurgitates, gut and fecal samples, homogenized body of the host organism, target of the diet study (for example with whole body of insects [6] ).
The DNA sequencing approach to be adopted depends on the diet breadth of the target consumer. For organisms feeding on one or only few species, traditional Sanger sequencing techniques can be used. For polyphagous species with diet items more difficult to identify, it is conceivable to determine all consumed species using NGS methodology. [5]
The barcode markers utilized for amplification will differ depending on the diet of the target organism. For herbivore diets, the standard DNA barcode loci will differ significantly depending on the plant taxonomic level. [7] Therefore, for identifying plant tissue at the taxonomic family or genus level, the markers rbcL and trn-L-intron are used, which differ from the loci ITS2, matK, trnH-psbA (noncoding intergenic spacer) used to identify diet items to genus and species level. [7] For animal prey, the most broadly used DNA barcode markers to identify diets are the mitochondrial cytochrome C oxydase (COI) and cytochrome b (cytb). [8] When the diet is broad and diverse, DNA metabarcoding is used to identify most of the consumed items. [9]
A major benefit of using DNA barcoding in diet assessment is the ability to provide high taxonomic resolution of consumed species. [10] Indeed, when compared to traditional morphological analysis, DNA barcoding enables a more reliable separation of closely related taxa reducing the observed bias. [11] [12] Moreover, DNA barcoding enables to detect soft and highly digested items, not recognisable through morphological identification. [13] For example, Arachnids feed on pre-digested bodies of insects or other small animals and their stomach content is too decomposed and morphologically unrecognizable using traditional methods such as microscopy. [14]
When investigating herbivores diet, DNA metabarcoding enables detection of highly digested plant items with a higher number of taxa identified compared to microhistology and macroscopic analysis. [15] [16] For instance, Nichols et al. (2016) highlighted the taxonomic precision of metabarcoding on rumen contents, with on average 90% of DNA-sequences being identified to genus or species level in comparison to 75% of plant fragments recognised with macroscopy. Morevoer, another empirically tested advantage of metabarcoding compared to traditional time-consuming methods, involves higher cost efficiency. [17] Finally, with its fine resolution, DNA barcoding represents a crucial tool in wildlife management to identify the feeding habits of endangered species and animals that can cause feeding damages to the environment. [18]
With DNA barcoding it is not possible to retrieve information about sex or age of prey species, which can be crucial. This limitation can anyway be overcome with an additional step in the analysis by using microsatellite polymorphism and Y-chromosome amplification. [19] [20] Moreover, DNA provides detailed information of the most recent events (e.g. 24–48 hr) but it is not able to provide a longer dietary prospect unless a continuous sampling is conducted. [21] Additionally, when using generic primers that amplify ‘barcode’ regions from a broad range of food species, the amplifiable host DNA may largely outnumber the presence of prey DNA, complicating prey detection. However, a strategy to prevent the host DNA amplification can be the addition of a predator-specific blocking primer. [22] [23] [24] Indeed, blocking primers for suppressing amplification of predator DNA allows the amplification of the other vertebrate groups and produces amplicon mixes that are predominately food DNA. [22] [25]
Despite the improvement of diet assessment via DNA barcoding, secondary consumption (prey of the prey, parasites, etc.) still represents a confounding factor. In fact, some secondary prey may result in the analysis as primary prey items, introducing a bias. However, due to a much lower total biomass and to a higher level of degradation, DNA of secondary prey might represent only a minor part of sequences recovered compared to primary prey. [26]
The quantitative interpretation of DNA barcoding results is not straightforward. [12] There have been attempts to use the number of sequences recovered to estimate the abundance of prey species in diet contents (e.g. gut, faeces). For example, if the wolf ate more moose than wild boar, there should be more moose DNA in their gut, and thus, more moose sequences are recovered. Despite the evidence for general correlations between the sequence number and the biomass, actual evaluations of this method have been unsuccessful. [5] [27] This can be explained by the fact that tissues originally contain different densities of DNA and can be digested differently. [28]
Mammals diet is widely studied using DNA barcoding and metabarcoding. Some differences in the methodology can be observed depending on the feeding strategy of the target mammal species, i.e. whether it is herbivore, carnivore, or omnivore.
For herbivore mammal species, DNA is usually extracted from faeces samples [29] [16] [30] [31] or rumen contents collected from road kills or animals killed during regular hunting. [15] Within DNA barcoding, the trnL approach can be used to identify plant species by using a very short but informative fragment of chloroplast DNA (P6 loop of the chloroplast trnL (UAA) intron). [32] Potentially, this application is applicable to all herbivorous species feeding on angiosperms and gymnosperms [32] Alternatively to the trnL approach, the markers rbcL, ITS2, matK, trnH-psbA can be used to amplify plant species.
When studying small herbivores with a cryptic life style, such as voles and lemmings, DNA barcoding of ingested plants can be a crucial tool giving an accurate picture of food utilization. [16] Additionally, the fine resolution in plant identification obtained with DNA barcoding allows researchers to understand change in diet composition over time and variability among individuals, as observed in the alpine chamois (Rupicapra rupicapra). [33] Between October and November, by analyzing the faeces composition via DNA barcoding, the alpine chamois showed a shift in diet preferences. Also, different diet categories were observed amongst individuals within each month. [33]
For carnivores, the use of non-invasive approaches is crucial especially when dealing with elusive and endangered species. Diet assessment through DNA barcoding of faeces can have a greater efficiency in prey species detection compared to traditional diet analysis, which mostly rely upon the morphological identification of undigested hard remains in the faeces. [23] Estimating the vertebrate diet diversity of the leopard cat (Prionailurus bengalensis) in Pakistan, Shehzad et al. (2012) identified a total of 18 prey taxa using DNA barcoding on faeces. Eight distinct bird taxa were reported, while previous studies based on conventional methods did not identify any bird species in the leopard cat diet. [23] Another example is the use of DNA barcoding to identify soft remains of prey in the stomach contents of predators e.g. grey seals (Halichoerus grypus) and harbour porpoises (Phocoena phocoena). [34]
DNA metabarcoding is a game changer for the study of complex diets, such as for omnivores predators, feeding on many different species with both plants and animal origin. [35] [36] This methodology does not require knowledge about the food consumed by animals in the habitat they occupy. [35] In a study on brown bear (Ursus arctos) diet, DNA metabarcoding allowed accurate reconstruction of a wide range of taxonomically different items present in faecal samples collected in the field. [35]
This section is empty. You can help by adding to it. (September 2020) |
This section is empty. You can help by adding to it. (September 2020) |
This section is empty. You can help by adding to it. (September 2020) |
A microsatellite is a tract of repetitive DNA in which certain DNA motifs are repeated, typically 5–50 times. Microsatellites occur at thousands of locations within an organism's genome. They have a higher mutation rate than other areas of DNA leading to high genetic diversity. Microsatellites are often referred to as short tandem repeats (STRs) by forensic geneticists and in genetic genealogy, or as simple sequence repeats (SSRs) by plant geneticists.
Phylogeography is the study of the historical processes that may be responsible for the past to present geographic distributions of genealogical lineages. This is accomplished by considering the geographic distribution of individuals in light of genetics, particularly population genetics.
Internal transcribed spacer (ITS) is the spacer DNA situated between the small-subunit ribosomal RNA (rRNA) and large-subunit rRNA genes in the chromosome or the corresponding transcribed region in the polycistronic rRNA precursor transcript.
Indel (insertion-deletion) is a molecular biology term for an insertion or deletion of bases in the genome of an organism. Indels ≥ 50 bases in length are classified as structural variants.
Forensic identification is the application of forensic science, or "forensics", and technology to identify specific objects from the trace evidence they leave, often at a crime scene or the scene of an accident. Forensic means "for the courts".
The subfamily Philanthinae is one of the largest groups in the wasp family Crabronidae, with about 1100 species in 9 genera, most of them in Cerceris; Alexander treats it as having only 8 genera. Historically, this subfamily has frequently been accorded family status. The subfamily consists of solitary, predatory wasps, each genus having its own distinct and consistent prey preferences. The adult females dig tunnels in the ground for nesting.
Genetic monitoring is the use of molecular markers to (i) identify individuals, species or populations, or (ii) to quantify changes in population genetic metrics over time. Genetic monitoring can thus be used to detect changes in species abundance and/or diversity, and has become an important tool in both conservation and livestock management. The types of molecular markers used to monitor populations are most commonly mitochondrial, microsatellites or single-nucleotide polymorphisms (SNPs), while earlier studies also used allozyme data. Species gene diversity is also recognized as an important biodiversity metric for implementation of the Convention on Biological Diversity.
The British Columbia wolf is a subspecies of gray wolf which lives in a narrow region that includes those parts of the mainland coast and near-shore islands that are covered with temperate rainforest, which extends from Vancouver Island, British Columbia, to the Alexander Archipelago in south-east Alaska. This area is bounded by the Coast Mountains.
DNA barcoding is a method of species identification using a short section of DNA from a specific gene or genes. The premise of DNA barcoding is that by comparison with a reference library of such DNA sections, an individual sequence can be used to uniquely identify an organism to species, just as a supermarket scanner uses the familiar black stripes of the UPC barcode to identify an item in its stock against its reference database. These "barcodes" are sometimes used in an effort to identify unknown species or parts of an organism, simply to catalog as many taxa as possible, or to compare with traditional taxonomy in an effort to determine species boundaries.
Environmental DNA or eDNA is DNA that is collected from a variety of environmental samples such as soil, seawater, snow or air, rather than directly sampled from an individual organism. As various organisms interact with the environment, DNA is expelled and accumulates in their surroundings from various sources.
Carol Ann Stepien is an American ecologist at the National Museum of Natural History of the Smithsonian Institution. She was elected a fellow of the American Association for the Advancement of Science in 2016.
According to the northern cryptic glacial refugial hypothesis, during the last ice age cold tolerant plant and animal species persisted in ice-free microrefugia north of the Alps in Europe. The alternative hypothesis of no persistence and postglacial immigration of plants and animals from southern refugia in Europe is sometimes also called the tabula rasa hypothesis.
Pollen DNA barcoding is the process of identifying pollen donor plant species through the amplification and sequencing of specific, conserved regions of plant DNA. Being able to accurately identify pollen has a wide range of applications though it has been difficult in the past due to the limitations of microscopic identification of pollen.
Landscape genetics is the scientific discipline that combines population genetics and landscape ecology. It broadly encompasses any study that analyses plant or animal population genetic data in conjunction with data on the landscape features and matrix quality where the sampled population lives. This allows for the analysis of microevolutionary processes affecting the species in light of landscape spatial patterns, providing a more realistic view of how populations interact with their environments. Landscape genetics attempts to determine which landscape features are barriers to dispersal and gene flow, how human-induced landscape changes affect the evolution of populations, the source-sink dynamics of a given population, and how diseases or invasive species spread across landscapes.
DNA barcoding is an alternative method to the traditional morphological taxonomic classification, and has frequently been used to identify species of aquatic macroinvertebrates. Many are crucial indicator organisms in the bioassessment of freshwater and marine ecosystems.
DNA barcoding of algae is commonly used for species identification and phylogenetic studies. Algae form a phylogenetically heterogeneous group, meaning that the application of a single universal barcode/marker for species delimitation is unfeasible, thus different markers/barcodes are applied for this aim in different algal groups.
Microbial DNA barcoding is the use of DNA metabarcoding to characterize a mixture of microorganisms. DNA metabarcoding is a method of DNA barcoding that uses universal genetic markers to identify DNA of a mixture of organisms.
DNA barcoding methods for fish are used to identify groups of fish based on DNA sequences within selected regions of a genome. These methods can be used to study fish, as genetic material, in the form of environmental DNA (eDNA) or cells, is freely diffused in the water. This allows researchers to identify which species are present in a body of water by collecting a water sample, extracting DNA from the sample and isolating DNA sequences that are specific for the species of interest. Barcoding methods can also be used for biomonitoring and food safety validation, animal diet assessment, assessment of food webs and species distribution, and for detection of invasive species.
Fungal DNA barcoding is the process of identifying species of the biological kingdom Fungi through the amplification and sequencing of specific DNA sequences and their comparison with sequences deposited in a DNA barcode database such as the ISHAM reference database, or the Barcode of Life Data System (BOLD). In this attempt, DNA barcoding relies on universal genes that are ideally present in all fungi with the same degree of sequence variation. The interspecific variation, i.e., the variation between species, in the chosen DNA barcode gene should exceed the intraspecific (within-species) variation.
Metabarcoding is the barcoding of DNA/RNA in a manner that allows for the simultaneous identification of many taxa within the same sample. The main difference between barcoding and metabarcoding is that metabarcoding does not focus on one specific organism, but instead aims to determine species composition within a sample.