Sixth form/ High School
Great Rift Valley – Schools Expeditions
Key features of the expedition:
- Opportunity to work with a Nature publishing team of academics on speciation mechanisms
- The only Opwall expedition that is run over 2 countries (Tanzania & Malawi)
- Chance to visit the Great African Rift Valley – birthplace of humankind – and learn about its ecology
- Learn to dive in Lake Malawi which has a greater diversity of fish than the Great Barrier Reef
Lake Malawi has the highest diversity of endemic fish species in the world with more than 650 species of cichlids. Normally, speciation occurs when two populations become isolated and adaptive changes, in their separate environments, cause the two populations to drift apart. After several thousand years, if the two populations meet again, they are so different interbreeding cannot occur. How does this happen in a lake? One theory is that changes in water level in the lake have caused separation into smaller lakes which have re-joined as water levels rose; but is this sufficient to see the huge diversity that appears in Lake Malawi? Studies in the volcanic crater lake, Lake Barombi Mbo, in Cameroon cast doubt on the possibility of speciation occurring only by geographical isolation. The crater lake is essentially a cone of water and therefore changes in water level could not result in separate lakes forming. However the dozen or so species of cichlid in this lake were revealed from DNA analysis to be more closely related to each other than to any other fish species, which suggests that speciation had occurred within the lake from a single founder species. The mechanism for sympatric speciation of this type still remains unknown.
North of Lake Malawi there are 14 crater lakes which provide an ideal natural laboratory to study how sympatric speciation might occur. Each lake appears to have been invaded independently by an ancestral species of Haplochromine cichlid from Lake Malawi, that has then speciated within the lake. The crater lakes have different habitats (e.g. depth, size) and different fish communities, yet are relatively simple systems compared to the much larger Lake Malawi so will hopefully provide clues as to how this speciation occurred. Samples of the fish from each lake will be taken back to UK universities for complete genome sequencing. In addition small numbers of live fish will be exported for mate selection studies.
Lake Malawi itself though is an important source of fish for the communities surrounding the lake. A series of standard transects to survey the fish communities around the Nkhata Bay area have been established to monitor population changes over time and determine whether fishing levels are sustainable. In addition to these direct observation surveys, fish landing surveys are also being conducted.
Structure of the expedition
This expedition is divided into three parts: 5 days working in western Tanzania with the team of scientists looking at how speciation occurs in lakes, 6 days dive training and/or helping with fish surveys in Lake Malawi and 2 days visiting the Liwonde National Park in Malawi to see some of the charismatic East African fauna.
Part 1 – Speciation mechanisms in crater lakes
The first 5 nights will be based in Masoko, south western Tanzania, helping with the under-surveyed volcanic crater lakes in the area. The groups will be split into smaller teams which will spend a day on each of the following activities:
- Fish surveys: This will involve setting and emptying fish traps at different depths as well as beach seining. The fish captured will be identified and morphometric measurements recorded.
- Limnology surveys: Helping to bathymetrically map the lakes and survey the water temperature and oxygen profiles at different depths.
- Aquatic invertebrate surveys: This will involve taking kick samples around the edge of the lakes and using grab sampling for the deeper areas to sample the aquatic invertebrate communities at different depths and on different substrates.
- Wildlife surveys of the lake surrounds: One of the objectives of the crater lake surveys is to highlight the area for potential tourist homestay visits. However for this to happen data need to be gathered on the birds and other wildlife around the lakes and communities. This survey will involve walking based surveys with an experienced naturalist. In addition, the students will be completing a lecture course on the Evolution of Species which covers much of the A-level, AP or IB syllabus on genetics and speciation but goes into more depth on the different mechanisms of speciation. Living in a small Tanzanian rural community will also give students the chance to learn about a different culture and community from their own.
Part 2 – Lake Malawi dive training and fishery research
For the next few days the group will be based at Njaya Lodge in Nkhata Bay, Malawi. The groups will be split into those learning to dive to PADI Open Water level, qualified divers helping with the dive based research surveys and snorkelers helping with other parts of the research programme.
Part 3 – Liwonde National Park, Malawi
On the final days of the second week the group will be transferred to the Liwonde National Park in Malawi. No visit to the Great Rift Valley is complete without seeing some of the large game species that provide such a draw for tourists to East Africa. The Liwonde National Park is the best national park in Malawi and it will give the group the chance to see many of the charismatic megafauna including elephant, hippo and rhino. A day will be spent in the camp and all students will experience a boat based safari and a vehicle safari with experienced local guides.
African Rift Valley Ecology and Evolution course
In addition to helping with the research projects during the day, the students will be completing a course on African Rift Valley Ecology and Evolution.
- The first part of this course which is taught by leading academics at the Crater Lakes site covers much of the A level, AP or IB syllabus on genetics and speciation but goes into more depth on mechanisms of speciation.
- The second part of the course gives an overview of the Rift Valley, fishery exploitation and the discoveries made about early hominids in this region and is taught at the Maru research centre.
- The final lecture in the course is given at the Liwonde National park and covers some of the management issues faced by large game reserves in East Africa.
Groups will be staying in a campsite, a short walk from the beautiful Masoko Lake. There are hammocks and tents, long-drop toilets and jungle showers at this camp. Living in a small Tanzanian rural community will also give students the chance of learning about local agriculture and experience living in a different culture and community from their own.
The groups are based at the Maru Lake Malawi Research Centre at Nkhata Bay on Lake Malawi. Accommodation here will be in shared rooms in buildings set in the grounds of the nearby lodge with shared bathrooms and shower blocks. There is a dining room and rest areas and a fully equipped dive centre on site set on a private beach.
For the final part of the expedition the students will be staying in the Liwonde Safari Camp. Accommodation will be in thatched dormitories with separate toilet and shower blocks in the camp.