eDNA surveying with the Natural History Museum

Martin Wells

The Natural History Museum's Biodiversity Officer Katy Potts tells us more about an exciting new survey method being used for the Brilliant Butterflies project.

There has never been more of an important time to understand biological diversity than the present. With an ever-changing climate and urbanisation on the rise, wildlife and biodiversity face consistent challenges to thrive in ever changing environments. It is therefore important that we understand the biodiversity that inhabits our landscapes. So, for land managers like London Wildlife Trust it is vital that they know what species are present on their sites so that they can manage the land for conservation for as many species as possible. It’s also important they monitor these species so that they can detect any changes in populations, whether that’s a decline in numbers of a particular species or change in its distribution.

Traditional methods of surveying invertebrates usually consist of an invertebrate expert going out onto nature reserves or sites and setting up a series of traps and undertaking surveys to collect a range of species across a range of invertebrate groups, unfortunately these groups are usually targeted already well studied groups. It then takes a considerable amount of time to process and identify the specimens collected. Most groups of invertebrates are difficult to identify, and it can take a lifetime to become an expert in one small subset of invertebrates, for example parasitic wasps, flies or beetles. The difference between species can be in the finest of details only visible under a microscope and it can take years to develop the skills to spot these differences. This is particularly important when species that are identical to the naked eye have their own environmental niches and use the environment in very different ways. Therefore, for land managers its vital to know which species you have in order to know the correct conservation methods to adopt. It takes a huge amount of effort, high level of expertise and vast length of time to accurately survey a nature reserve. All of this presents a big challenge for the conservation of invertebrate communities. This is where Brilliant Butterflies hopes to make a change using exciting DNA technology called environmental or eDNA.

eDNA surveying taking place

What is eDNA?

We can think of DNA as the blueprint to all life forms, each individual species has its own unique DNA sequence which allows us to determine each individual species. So, what do we mean when we refer to eDNA? eDNA stands for environmental DNA and this is the DNA that is released from an organism into its environment. This may be due to an insect dying and its DNA being released into the soil, or simply by an insect waking through a particular area, leaving tiny fragments of its DNA behind as It passes. This is great for us as scientists as it means we can take eDNA samples from soil, water, air and snow and detect what species were present in that area in the past.

Various survey equipment on grass

The Natural History Museum’s eDNA fieldwork

The  Natural History Museum are working in partnership with London Wildlife Trust on the Brilliant Butterflies project. The team are undertaking eDNA surveys of the project nature reserves to assess the invertebrate populations on the sites. We are doing this by setting up Malaise traps which are tent like structures that intercept flying invertebrates (see top photo). We place them along invertebrate flight paths in order to get a good indication of the flying invertebrates on the sites. Alongside this we are also setting up pitfall traps which are like small containers like cups which are placed into the ground to collect the ground dwelling invertebrates. Both techniques collect the invertebrates into molecular grade alcohol that preserves their DNA. When we are digging the pitfall traps were are also taking soil samples to analyse for the traditional eDNA survey, assessing the DNA that is present in the soil. With the malaise and pitfall samples we are pioneering new methods in eDNA by analysing the alcohol that the specimens have been collected in.

Both myself and Steph Holt recently spent two wonderful weeks setting up traps on the chalk grassland reserves across Croydon and Bromley. The traps were set up and left for one week to collect an array of invertebrates present on the sites. They were then taken down the following week and the samples were then frozen to prevent any of the DNA from degrading and transported to the museum’s molecular facilities ready for analysis by museum expert Andy Briscoe.

Two people sit on grassland surveying

What does this mean for invertebrate conservation?

Having a solid undertaking of what species are present on nature reserves is imperative, particularly the smaller, understudied groups and how they impact ecosystems as a whole. New survey methods like the eDNA surveys may be transformative in how we assess nature reserves. Without collecting a small subset of species in surveys like these we will never know what invertebrates are present on the sites and therefore how to manage the land for their conservation and longevity.

Find out more about Brilliant Butterflies

London Wildlife Trust has partnered with the Natural History Museum and Butterfly Conservation on the Brilliant Butterflies project which is creating and restoring butterfly habitat across South Croydon and Bromley, thanks to players of the People’s Postcode Lottery.

BB logo lock up