India testing eDNA technology for biodiversity assessment

The Zoological Survey of India (ZSI) is testing new technology to assess biodiversity using environmental DNA (eDNA), as reported by Mongabay-India. The ZSI) has set up a pilot project to use eDNA (environmental DNA), to study and monitor wildlife.

The Mongabay-India highlights that at present, researchers collect scat (faecal) material from animals and take them for identification. This is done in the areas they are studying. The DNA of the particular targeted species is then sorted out for population estimation. However, a study in ‘Current Biology’ by scientists from the United Kingdom has stated that air-quality networks collect environmental DNA with the potential to measure biodiversity at continental scales and that these samples have ‘surprisingly stable DNA,’ and it is the best possible method to ascertain terrestrial biodiversity.

According to the United States Geological Survey (USGS), eDNA is organismal DNA that can be found in the environment. DNA, short for deoxyribonucleic acid, is the hereditary material in organisms that contains the biological instructions for building and maintaining them. The chemical structure of DNA is the same for all organisms, but differences exist in the order of the DNA building blocks, known as base pairs. Unique sequences of base pairs, particularly repeating patterns, provide a means to identify species, populations, and even individuals. eDNA originates from cellular material shed by organisms (via skin, excrement, etc.) into aquatic or terrestrial environments that can be sampled and monitored using new molecular methods. Such methodology is important for the early detection of invasive species as well as the detection of rare and cryptic species.

The ZSI’s pilot project, based on this study, will do this through air quality monitoring stations, set up by various government authorities, which are used to identify and collect particulate matter present in the air. Based on the particulate matter present or collected on filters, the levels of pollution in the air are determined after processing and analysing filters in the lab. The UK study also added that “air monitoring networks are in fact gathering eDNA data reflecting local biodiversity on a continental scale, as a result of their routine function. In some regions, air quality samples are stored for decades, presenting the potential for high-resolution biodiversity time series. With minimal modification of current protocols, this material provides the best opportunity to date for detailed monitoring of terrestrial biodiversity using an existing, replicated transnational design and it is already in operation.”

The USGS website states that protocols using eDNA may allow for rapid, cost-effective, and standardized collection of data about species distribution and relative abundance. For small, rare, secretive, and other species that are difficult to detect, eDNA provides an attractive alternative for aquatic inventory and monitoring programs. Increasing evidence demonstrates improved species detection and catch-per-unit effort compared with electrofishing, snorkelling, and other current field methods. Thus, detection of species using eDNA may improve biodiversity assessments and provide information about status, distribution, and habitat requirements for lesser-known species.

Further, the USGS website says that the eDNA may also be an effective tool for early detection of aquatic invasive species. Application of eDNA methods for invasive species monitoring may include periodically collecting water samples and screening them for several invasive species at once. Boat-ballast water, a source of introduction for many invasive species including molluscs, also could be sampled. Some intensive eradication programs for invasive species fail when a few surviving individuals recolonize the ecosystem. eDNA methods may provide a means of confirming eradication of all invaders.

The Mongabay-India report points out that that the UK study states that for a biodiversity-rich country such as India, which is battling conservation issues including a massive problem of invasive species threatening natural and agricultural landscapes, it can contribute significantly.