(Biological Sciences PhD, 2019)
What I loved most about my PhD was the fieldwork. It was fantastic spending so much time in the rainforest. Every day you knew there was a real chance of seeing elephants, eagles, hornbills, monkeys, pythons, bears (we saw them all), and that’s so exciting.
You did your PhD in Molecular Ecology and Conservation at Queen Mary. What was the focus of your research and what attracted you to this particular field?
My PhD was on the feeding ecology of insectivorous bats in Borneo, and how this differs between areas of forest that were selectively logged, and areas which haven’t been logged in historic times. My background was in conservation biology, tropical dietary ecology, and DNA barcoding, and so the topic was the perfect mixing of my skills. My PhD took place within the ‘Lombok’ consortium, a group of researchers working on everything from soil microbes to large mammals, creating a big picture on how to best balance agriculture and conservation. Being part of a wider research-group was attractive to me, as it made it more likely that my research would have real-world consequences.
How did you conduct your research and what were your overall findings?
I was part of a team in the rainforest, in particular working with aluma Tor Kemp and several local research assistants. Over three years I spent about 10 months living in the forest, handling over 2,000 bats. We would catch bats in traps, then leave them in small cloth bags for a while. We put any poo they left behind into sterile tubes, and I then analysed those samples using ‘DNA metabarcoding’. Briefly, this is where a sample of many animal groups (the insects in the poo) are amplified using PCR, then sequenced. This generated a huge number of sequences from the insects fed on by the bats. Using this data I created networks of interactions: essentially a food web where I know bat species A feeds on 300 prey groups, bat species B feeds on some of the same prey, but also 120 different ones, etc. By combining this information from many bat species we can measure characteristics of a network and assess questions about that ecosystem. We knew many bat species persist in areas of logged forest, but little about their feeding ecology and its relationship to their long-term persistence. At its most basic, a bat feeding on hundreds of species is less vulnerable to extinction than a bat which feeds on three: the latter could become locally extinct if some of their prey species crash, but the former has more alternative options.
Most bats studied consumed fewer prey groups in the logged than unlogged areas. We don’t know if this is due to fewer prey being available, or because of differences in bat foraging, but they are more vulnerable to fluctuations in their prey as they already have fewer of them in their diets. This is also shown in the networks of bats and prey. We know that these areas of logged forest remain important for bat conservation, but we showed they are more ‘brittle’, and future disturbances such as extreme weather or habitat fragmentation could damage bat populations in logged more than in unlogged areas.
I was within a wonderful community of PhD students at Queen Mary, and my supervisors were great. These influences led to me becoming a proficient programmer and bioinformatician, despite having zero experience with these techniques beforehand, and these are the main skills I use in my current role!
What are some of the stand-out moments from your PhD and your time at Queen Mary?
The main one is fieldwork: it was fantastic spending so much time in the rainforest. Every day you knew there was a real chance of seeing elephants, eagles, hornbills, monkeys, pythons, bears (we saw them all), and that’s so exciting. I also had the phenomenal privilege of handling thousands of unusual bats. I made great friends while out there: field stations are a mixing-pot of oddballs who decide to spend their days studying exciting biodiversity, despite being perpetually damp and feeding hundreds of leeches…
I was also within a wonderful community of PhD students at Queen Mary, and my supervisors were great. These influences led to me becoming a proficient programmer and bioinformatician, despite having zero experience with these techniques beforehand. These are some of my main responsibilities in the role I’ve been working in since completing my PhD!
How did your PhD and your time at Queen Mary act as a springboard for your current role as Postdoctoral Researcher at the University of Oxford for the research consortium Target Malaria?
My current position has been a straightforward progression from my PhD at Queen Mary: at Queen Mary I used DNA metabarcoding to study interactions between bats and their prey. I now use DNA metabarcoding to study the interactions of a mosquito species… including when they are eaten by bats.
At Queen Mary I learned how to capture bats, collect samples from them, process them in a laboratory, handle sequencing data, create ecological networks, analyse these complex datasets, write it up and then publish it… These are key parts of my current role as part of the ecological observatory study.
Tell us more about this role. What does it involve and what are some of your day-to-day activities?
I work at the University of Oxford; we are one of the eleven research institutions that form part of the consortium Target Malaria, a vector control research alliance. Target Malaria brings together over 200 researchers and professionals from Africa, North America and Europe aiming to develop and share new genetic technologies to reduce malaria transmission.
Malaria is caused by a parasite called plasmodium, which is transmitted by bites from female Anopheles mosquitoes. Female mosquitoes feed on blood to obtain protein for egg-laying, and when they bite somebody infected with malaria they may ingest the parasite, which can be transmitted to people they bite later.
The ‘gene drive’ mosquitoes being developed by Target Malaria are intended to reduce numbers of Anopheles in the wild, therefore reducing malaria transmission. A ‘gene drive’ is a form of genetic modification which lets us increase the probability of an animal passing a gene of interest to its offspring. We are genetically modifying mosquitoes to affect their reproductive capacity to reduce their population and control malaria transmission.
Target Malaria are keen to answer the question that this raises: “what would the ecological impacts be of reducing a mosquito species?” This is where the ecology team come in: our field team at the University of Ghana, another Target Malaria partner institution, have been collecting data on the ground that will lead to the creation of ecological networks of how the different organisms in the ecosystem interact with Anopheles gambiae. This will enable us to understand the role of these mosquito species in the ecosystem and accurately model how current interactions would change if their numbers were to be reduced or disturbed. This library of reference sequences will be used to classify samples of ecological interactions, which we’ll be processing in the same way as those from my PhD. By creating large ecological networks involving Anopheles gambiae, we can then simulate the impacts of greatly reducing the abundance of the mosquito species. I’m one of three postdoctoral researchers on this project, and so my role involves experimental planning and data analysis. Find out more about Target Malaria's work.
You shared the alarming statistic that Malaria infects over 200 million people a year, killing around half a million, the majority of victims being children under 5 years old, primarily in Africa. What are some of the possible ecological impacts of reducing malaria mosquito populations in Africa and elsewhere?
We know that mosquitoes are food for many animals, coexist and compete with many more, and may be pollinators, so it’s important to ask what impact reducing their numbers could have. No studies have solely reduced the Anopheles mosquitoes that spread malaria, but we can learn lots from previous campaigns of insecticide-use and habitat modification. So far there have been no large effects observed of reducing Anopheles using those techniques, though they may have a greater ecological impact than a gene drive approach, as the species which exist alongside Anopheles are harmed by actions such as insecticide-spraying (such as bees).
While other animals do feed on or compete with Anopheles, they live in extremely biodiverse areas and so are a small part of a big picture. Even a large swarm of 1,000 mosquitoes only weighs about 0.2 grammes, so Anopheles are assumed to be unimportant to the predators that sometimes feed on them: they don’t contribute enough to be a key food for any animal. As an analogy, I eat chocolate eggs at this time of year, but they’re a small enough part of my nutrition that we assume I won’t starve in their absence.
We’re checking if they act as pollinators, as much of adult Anopheles diet comes from feeding on nectar. Again, there are many pollinators which they exist alongside and no evidence that Anopheles are key pollinators of any plants.
It’s also possible, though unlikely, that Anopheles outcompete other pest species in their habitats. If this were the case and Anopheles were greatly reduced, those species would be ‘released’ from competition and may pose new threats to human health. We’re exploring this with our current research. While it’s unlikely, we still need to investigate any potential routes to harm.
Malaria is an awful disease: it kills over half a million people per year and infects over 200 million. Those that survive have suffered a horrible illness, and every premature death is a tragedy which humanity must try to prevent.
What are some of the difficulties and obstacles you encounter in your research?
On a personal level, the project is technically ambitious and my job is a satisfying but difficult challenge. A lab technician and I are responsible for working on a huge range of samples. We’ve been designing protocols, and I process the large and varied datasets we generate, often on the university’s high-performance computers. It’s a big step up from life as an early PhD student who’d never done any of this!
Target Malaria’s mission is difficult both in the basic science and its implementation: our aim is to reduce the numbers of a species by releasing modified mosquitoes into the wild in multiple countries. It’s crucial that this is known to be safe and takes place under the relevant regulatory frameworks and with the full informed agreement of stakeholders affected by the project. There are sadly disinformation campaigns targeting any work involving genetic modification, and so it’s key that we continue to demonstrate with research and data that the techniques that we are using will be safe. It’s important that the science of our work is clearly communicated: while ‘genetic modification’ sounds new and scary, humanity has been genetically modifying other organisms since we began farming and domestication. The main difference is we can now do this in a more precise and targeted way, while continuously testing implications of the changes that we make. The modified genes can only be spread through sexual reproduction, and so cannot spread beyond Anopheles.
After decades of steady reduction in the incidence of malaria, progress has recently stalled, putting more people at risk. Why do you think this is?
Malaria is a constantly moving target. Previous interventions typically relied on insecticides, sanitation and habitat modification, and while they remain fantastic tools, both inevitably have downsides. Mosquitoes and plasmodium are evolving resistance to the drugs and insecticides we’ve used, reducing their efficacy. And both insecticides and habitat modification require repeated interventions over large rural areas, which is difficult logistically and financially. These factors are sadly combining to halt the progress that has been made against malaria in other regions. Our current techniques will remain important parts of our toolkit, but we hope that adding an effective new one brings us closer to a world without malaria.
Monday 25 April marks World Malaria Day which aims to highlight the need for continued investment and sustained political commitment for malaria prevention and control. Why is it important that we continue our fight against Malaria?
Malaria is an awful disease: as you mentioned above it kills over half a million people per year and infects over 200 million. Those that survive have suffered a horrible illness, and every premature death is a tragedy which humanity must try to prevent. A third of the world’s population is at risk of malaria, with this expected to increase as climate change expands the range of the Anopheles mosquitoes. Allowing this situation to continue is unconscionable, allowing it to worsen is even more so. We can fight against malaria and so it is profoundly important that we do so.
Finally, is there anything people find surprising or admiring about you?
People might be surprised that I have ADHD: there’s many negative stereotypes and poor awareness of what it entails, and so it can be surprising that somebody with ADHD is a scientist with a PhD, working at Oxford University. The condition (‘attention deficit hyperactivity disorder’) is poorly-named: it isn’t so much a deficit of attention or the presence of hyperactivity, rather it’s issues with regulating attention and energy. No two people have identical symptoms, but common examples include difficulty focussing (unless something is interesting and then being unable to focus on anything else, aka ‘hyperfocus’), listening, or staying still. It’s thought that around 4% of the world’s population have the condition and we can be found in all walks of life. I suspect that people with ADHD are overrepresented in academia, as the role can select somewhat for those who hyperfocus on questions that they’re into. However, diagnosis and treatment can be lifesavers, as when left undiagnosed it’s highly correlated with mental health issues like depression and anxiety, and ‘negative life outcomes’ such as divorce, addiction and job-loss. If anyone reading this wonders if they may have the condition, I’d strongly recommend looking into it. There are a lot of resources available online, but as a start the YouTube channel ‘How to ADHD’ is great. Visit the How to ADHD YouTube channel.
If you would like to get in touch with David or engage him in your work, please contact the Alumni Engagement team at alumni@qmul.ac.uk.
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