Documenting the incredible diversity of southern Africa
Professor David Bilton has spent almost two decades working to understand the complex and unique species inhabiting the southern tip of Africa
"The Cape region is one of the most biodiverse places on earth, for many groups the most diverse place outside the tropics. It’s a great place for students to experience and be in when thinking about ecology and evolution, giving them first-hand experiences they can draw on during the rest of their degree."
Professor Bilton underneath the Wolfberg Arch in the Cederberg
My initial interest in working in Africa was sparked by the apparent diversity of the fauna and the fact that southern Africa hosts an unusual combination of animals and plants, with different evolutionary origins. These include taxa which originated on the old southern supercontinent of Gondwana and are now scattered across the southern hemisphere landmasses in places like southern Africa, southern South America, Australia and New Zealand. Through genetic work, we’ve recently found that some of the Cape water beetle lineages seem to have their closest living relatives in New Zealand, for example.
In addition there are some groups which instead have a northern hemisphere origin and have spread through Arabia and Ethiopia, then down the Eastern Arc mountains in Africa, into the Cape (probably in periods of colder climate), where in many cases they have radiated due to the availability of temperate habitats. We’re just describing a new species of diving beetle, for example, known from a small area close to Cape Agulhas, the most southerly point in Africa. Apart from a few species in South Africa, Kenya and Ethiopia, most of its relatives are in Europe, northern Asia and North America.
Finding biodiversity near Cape Town
Initially I started work on water beetles in South Africa as a result of us running the Marine Biology and Coastal Ecology field course to West Coast National Park in the Western Cape Province, just north of Cape Town.
My first work was focussed on Aspidytes niobe, a beetle only found crawling around in trickles on wet mountain rock faces in the far southwest of the Western Cape. There is one other living species in the whole family, and that’s in similar habitats in central China.
Summit rockpools on Table Mountain
There are Jurassic fossils of similar beetles from various parts of central and south Asia and living species therefore seem to be real relicts, in an evolutionary sense. I am one of only two people ever to find the South African species in the field (a number of others have tried and failed) and I first found the larvae and have co-authored a number of papers on these unusual beetles.
At the same time I found a number of species clearly new to science, making me realise that despite being well worked in comparison to many parts of Africa, the South African fauna remained incompletely known. This sparked my continued interest and I have now been to the region once or twice every year since 2008.
Sampling a seepage on the Wild Coast
Uncovering new biodiversity hotspots
I’ve conducted fieldwork on water beetles in most parts of the country now, probably covering more sites and regions than anyone else previously. I’ve particularly focussed on the Cape Floristic Region, since this is the area with the most diverse and unusual biota. Over the years we’ve sampled widely in this area and outside, concentrating on mountains and other areas which act as ecological ‘islands’, as these are more likely to host unusual species.
Elsewhere, we’ve visited the high peaks of the Drakensberg, isolated mountain systems in the middle of semi-arid Karoo region, tropical wetlands in KwaZulu-Natal, close to Mozambique and subtropical grasslands and forests on the Wild Coast. In short, getting to lots of stunning and relatively pristine environments and usually being the first people to explore the aquatic fauna.
On some occasions, I’ve been joined by other University of Plymouth colleagues, including Andy Foggo, who’s spent a lot of time trying to catch very small beetles on wet rock faces, but did end up getting a beetle (Mesoceration foggoi) named after him for his efforts! In the course of my work I’ve also developed strong research links with biologists in Albany Museum/Rhodes University in Grahamstown and at the University of Johannesburg and in recent years we’ve undertaken joint field trips,extending the focus to include other elements of the aquatic fauna, including freshwater crabs. I also hold a Visiting Professorship at the University of Johannesburg.
NEWS RELEASE: Scientists discover freshwater diversity hotspot in arid region of South Africa
What makes South Africa so special?
At a country scale, a lot is down to the wide range of climatic and therefore ecological conditions present. South Africa hosts everything from semi-deserts to warm subtropical forests and wetlands. Of all regions, the Cape is probably most diverse; why exactly this is the case is not entirely understood, but ultimately a lot of the explanation may be down to relative climatic stability, over relatively long timeframes, meaning rare species are less likely to go extinct.
Coupled with a number of factors which are likely to promote speciation, in some groups at least, you end up with high levels of biodiversity, since the number of species in a region is in the end determined by a balance between speciation and extinction.
Sampling a natural wetland close to Cape Agulhas, the most southerly point in Africa
In 2015, Professor Bilton published research about Capelatus prykei, a beetle so different from any of the world’s other diving beetles that it was placed in a new genus all of its own
NEWS RELEASE: New species of diving beetle found living in isolation in Africa
The first specimens were sent to us by James Pryke, who is now an academic at Stellenbosch University – he found them when he was doing his PhD on wetlands around Cape Town. Clive Turner (one of the co-authors on the Capelatus paper) and I recognised pretty much straight away that this was something really unusual, owing to its relative size and shape and the scratches on its wing cases. Initially we thought it must be known already, but clearly we couldn’t find anything to match. We were then both in the Natural History Museum in London, and looked through the drawers of un-named diving beetles. There are thousands of un-named specimens, that no-one has got around to working on, but most of these, even if they may in some cases be undescribed species, are in known groups – so not that unusual really.
Scanning the collection drawers, we spotted a series of 12 specimens of this beetle, collected in the 1950s from very close to where James got his beetles, but in an area which is now covered by settlements on the edge of Cape Town. At this point we were sure we had something interesting. Around the same time, we got James to send a fresh specimen for DNA sequencing, which allowed us to see where this beetle fits into the radiation of diving beetles. I also visited the area James collected Capelatus and worked out its habitat requirements. I’ve found it at the type locality a couple of times, but nowhere else at all, despite looking. One thing I really like about this beetle is that to the uninitiated it just looks like yet another black diving beetle, but in reality is something quite special!
Canthyporus namaqualacrimus
Parhydraena cataractae
Yola matsikammae
I’ve described over 50 new species - three woodlice (one of which was from Dartmoor), all the rest water beetles. I probably have around that number still waiting to be worked through or in the process of being published. It is modest when one considers that there are probably at least 2million undescribed beetles on earth, but a fairly significant contribution to our understanding of the Cape fauna as most of the beetles are from South Africa.
Mesoceration foggoi
Sebasthetops omaliniformis
Coelometopon glenavoni
Plans for future research
As well as continuing to explore new areas and habitats, we are developing two additional lines of research. In both cases these are only possible due to taxonomic work we’ve been doing and the detailed knowledge of the fauna this has brought. One line of investigation is disentangling the evolutionary history of some of the key groups in the Cape water beetle fauna, which will be the first time really this has been attempted on this scale for animals.
We particularly want to understand where the closest relatives of Cape lineages can be found and why some taxa are so diverse in the Cape – is there any evidence of high speciation rates and/or low extinction? Second, we want to extend work we’ve done in Europe on the role of physiology in setting geographical range limits to southern temperate taxa in southern Africa. We suspect that the southern temperate groups are, for a number of reasons, likely to be more sensitive to climate change than their northern hemisphere equivalents, but no-one’s really tested this to date. In both cases I’ll be working with colleagues in South Africa and elsewhere.
Involving students in research
One of the places we do our field work in the National Park has turned up two new water beetle species, one of which is still known only from this one lagoon. Students get the chance to see these each year, alongside many other species only found in the Western Cape, some of which are pretty odd. There is a ‘dung’ beetle which has switched to feeding on freshly dead giant millipedes rather than animal dung, and bladder grasshoppers – the males of these have swollen gas-filled abdomens that one can see through, which act as amplifiers. There are also many species of giant limpets that carpet the rocky shores and are pretty special, as are the huge isopods (like giant woodlice) feeding on washed up kelp. Really strange animals.
In their final year our students can learn more about what exactly species are and how they evolve in a final year course I teach on these topics, something which does include some of my research.
I also give the students the opportunity to see some of the new taxa I’ve named, including type specimens, something which proves very popular and is unique in their degrees. Our second year field course is about biodiversity; what it is, how you study it and what generates it – including why some places much more diverse than others.
Marine, freshwater and terrestrial habitats are special in this area, and they get to do hands-on work in all three.
The Marine Biology and Ecology Research Centre (MBERC)
Members of the MBERC address a broad range of research questions, from the effects of environmental stress on microbes and developing embryos to the management of large scale impacts, such as global climate change.
BSc (Hons) Marine Biology and Coastal Ecology
Have you ever wondered why animals live where they do, why coral reefs are so diverse, or how to conserve our increasingly threatened marine life? This world-leading degree challenges you to ask these questions and more.
You’ll access some of Europe’s best marine facilities, where our experts will help develop your skills on coasts packed with biodiversity.
