Ground beetles, such as Mouhotia batesi, are among the most species-rich groups of animals. © Jamikorn Sooktaramorn/ Shutterstock
Describing new species can take decades. But scientists are working to identify new ways to speed up our understanding of this hidden biodiversity.
By looking at the genetic data of thousands of beetle species, our researchers are able to reveal the true breadth of tropical ground beetles in a move that could help save their rainforest homes.
Earth’s biodiversity is vast, with around 2.1 million species named so far.
However, with estimates of the overall number of species ranging from five to 10 million, there are far more species that we don’t know about than those we do.
This gap in our knowledge has serious impacts for how we understand and protect the planet. If a site contains many species that haven’t yet been named, and only some that have, then it’s much less likely that it’ll be considered for conservation action.
As describing a species is a long process, one way to tackle this issue is to focus on genetic data instead. A new paper led by Dr Beulah Garner, one of our entomologists, used this approach to assemble a new family tree of ground beetles in the family Carabidae, a widespread but poorly understood group of insects.
“Our world is changing rapidly, so many species are becoming extinct before they’re even named,” Beulah says. “While traditional taxonomic methods are still important, molecular data means we can recognise the diversity of species in an area before they’re formally described.”
“By taking DNA samples during fieldwork, we’re able to place them on a family tree that gives us an idea of how many putative species might be living in an area. This provides a quick way of understanding diversity in threatened habitats to help gain a more complete understanding of biodiversity on Earth and focus conservation efforts where they’re needed most.”
The research, published in the journal Systematic Entomology, represents the largest and most comprehensive effort to understand the relationships of the ground beetles to date. It has helped to resolve some longstanding taxonomic puzzles about these insects which will help to improve the wider understanding of the group.
By combining this with information about where species live, the team hopes the tree will also help to target the lineages and areas in which they live that need the most protection.
PhD student Aileen Scott, who co-led the research, adds that “there’s still work to be done” to understand these beetles.
“We’ve only just touched on the geographical evolution of the family in this paper and plan to research this more thoroughly in the future,” explains Aileen. “Ongoing sample collection and DNA sequencing in our lab group will help to address this, as well as resolving uncertainty around the placement of a small number of taxa.”
The Agra beetles, such as Agra grace, are among the largest genera of ground beetles. Image © Terry Erwin via Zookeysopens in a new window, licensed under CC BY 3.0opens in a new window.
Ground beetles are one of the most diverse groups of animals in the world, with around 40,000 species named so far. These include animals with a variety of different lifestyles, from bombardier beetles with their powerful chemical defences to blind cave-dwelling species and others which sequester poison from their prey.
The sheer number of these beetles means that most people on Earth are never far from one. However, their extraordinary diversity also means that it’s a challenge for scientists trying to study them.
“One of the biggest ground beetle genera is called Agra,” explains Beulah. “There are probably more than 1500 species of these canopy-dwelling insects, which have a distinctive metallic sheen and elongated bodies adapted for hunting.”
“Unfortunately, the taxonomic expertise for these beetles and many others is dying out. It reflects a wider taxonomic deficit in science at the moment, where there just aren’t enough people who understand groups well enough to name new species.”
As a result, during fieldwork in the tropics it’s not uncommon for Beulah to see what are probably new species. But, as it can sometimes take 100 years from a specimen being collected for a species to be named, Beulah also knows she probably won’t have time to name them.
“It can be quite disheartening,” Beulah admits. “Knowing that there are so many undescribed species out there but that these species will probably never be named in your lifetime is a really bittersweet feeling.”
We look after many different ground beetle specimens, including this Laemostenus complanatus, which help scientists to uncover the relationships between known and unknown species. © The Trustees of the Natural History Museum, London
While these species wait to be named, Beulah and her colleagues have turned to genetic data to understand the diversity and distribution of the ground beetles.
In particular, they’re focusing on the DNA found in the mitochondria – the part of the cell that generates energy from sugar. Mitochondria have their own genome which is kept separate from the nuclear DNA of the animal and which are known to pick up changes much more quickly.
One particularly useful section is known as the genetic barcode due to the differences it can highlight between even close relatives. This means it can be used to distinguish between different species, even if they haven’t been named yet.
Using data gathered from DNA databases and from more than a decade of fieldwork in threatened tropical biodiversity hotspots, the researchers were able to assemble a family tree containing more than 7,000 named and potentially new ground beetle species.
It shows that these insects are all descended from a common ancestor, allowing the team to divide them into smaller groups that help to better understand them. It also allowed the researchers to begin appreciating the true scale of ground beetle diversity in the tropics, which is poorly understood.
“Linking geography to the relationships between these species is a quick way of understanding how threatened they are,” adds Beulah. “Policymakers need evidence when they’re making decisions about conservation, and while this approach isn’t definitive, it can enhance an argument for habitat protection.”
Yet, a key problem of molecular taxonomy is the need to link the sequences to the known species diversity. “The work of taxonomists has changed dramatically since the major collections built in colonial times,” says Professor Alfried Vogler, the senior author of the paper.
Museum collections are now our only direct access to the historic record of how the abundance and diversity of different animals are changing. They also contain the specimens and genetic material that can help to put names to many unknown species from the recent DNA studies.
How many of these species still exist, and how we recognise them in our molecular sequencing, poses a challenge for modern taxonomy. But together, this mixture of taxonomic tradition and cutting-edge innovation will be essential to save countless animals, plants, fungi and so much more, even if we don’t know about them yet.
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