Research on genetic health of forest fig trees

Ficus trees are an essential source of food in forests because they produce fruit year-round. However, South African forests have been fragmented into tiny pieces since before the ice ages.

This long-term fragmentation can destroy the genetic variation in populations. But, fig trees are pollinated by fig wasps that can carry pollen over vast distances (the record is 160 km far). This is even though fig wasps only live for a few days and are just over one millimetre in length. This impressive feat is accomplished by the wasp using wind currents to move them over tens of kilometres and volatiles that attract wasps to trees ready to be pollinated.

A team of researchers consisting of Junyin Deng (PhD student) with her supervisors: Jaco M Greeff, Simon van Noort (South African Museum), Steve G Compton (Leeds University) and co-worker, Yan Chen (Mianyang Normal University) recently researched the genetic health of three Ficus species that grow in South African forests. This was done by looking at their genetic structure.

"Two of these species are forest specialists, and the third is a generalist that also occurs outside forests. Unsurprisingly, the generalist species showed very little genetic differentiation between forests because the trees occurring between forests are stepping stones for gene flow between forests. For one of the forest specialists, it seems that wasps can connect forests genetically. This species' nuclear DNA is healthy, looking like that of a large population."

According to Greeff, "The same is, however, not true for their cytoplasmic DNA which is extremely homogenous within populations and differs strongly between populations. This could be remedied by transplanting seeds between nearby forests. On the other hand, the other forest specialists have genetic differences even between far apart trees in one forest. Therefore, we suspect its wasp behave very differently to avoid being blown to their death. As a result, these populations can only be saved if seeds are planted in nearby forests, even if they lack the species.

Researchers

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  Prof Jaco M Greeff

  He leads a small research group at UP (with international ties) that is investigating “two things that offer different benefits”: fig wasp sex ratios and Afrikaner genetic heritage.
  
  “In fig wasps, we are trying to understand fig wasp sex ratio variation and in Afrikaners, we are looking at their maternal genetic heritage,” Prof Greeff says.
  
  “Fig wasp sex ratios give us an understanding of our place in the world – basically, an understanding of how our actions can affect natural selection and how natural selection affects our actions. The latter is crucial to understanding why we are messing up the planet we depend on. Unfortunately, it cannot stop our ruinous behaviour, but we can at least understand that we must guard against our own nature to nurture humans and all other life on the planet.”
  
  His second subject is Afrikaner genetic heritage. “This work has shown that Afrikaners are not an uber white race, but are actually the result of a mixture of Europeans, slaves from Africa and Asia, and local Khoekhoe and San populations. I hope this will show that Afrikaners are a unique African population and that they and other South Africans will learn to be proud of this.”
  
  Prof Greeff has been involved in cross-faculty research with his wife, Sarah Clift, at UP’s Faculty of Veterinary Science. They were studying a worm that infects dogs; he hopes to pick up this work again in the future.
  
  Prof Greeff’s most important recent research contribution is a review on sex ratios in fig wasps; he also wrote an essay on this for The Conversation. As for the topic of Afrikaner genetic heritage, a paper in BMC Biology was a recent highlight; The Conversation also published the lay summary of this work.
  
  Prof Greeff says his honours supervisor introduced him to the amazing world of fig wasps and his PhD supervisor introduced him to evolutionary biology. “These two academics are genuinely interested in how life works and are not driven by attaining personal fame,” he says. “Evolutionary biology has been the lens through which I have come to see life, and fig wasps are the super organisms I have studied for more than 20 years.”
  
  Prof Greeff hopes to persuade other researchers that fig wasps are useful model organisms with which to study sex ratios, although their sex ratios have not been explained adequately. He would also like to explain the broader implications of evolutionary biology to the layperson. As for his work on Afrikaner genetic heritage, Prof Greeff would like all South Africans to embrace the reality that Afrikaners are uniquely African.
  
  As to why his research matters, he says: “We have a view of life that everything is there for a divine purpose. In the era of science, this view is still very much embedded in our psyche. It gives most people a comfortable feeling that nothing can go wrong, that we cannot rubbish the planet and that there is some sort of master plan. The most important point of my work is that nature is surprisingly corruptible – not everything is perfectly designed; organisms like humans can evolve and utterly destroy the very planet they depend on.”
  
  His advice to school learners or undergraduates who are interested in his field is to question everything, especially things that are presented as facts or truths. “Once you start asking questions, do not stop; continue to scratch like a terrier that is convinced there is a rat just out of reach.”
  
  In his spare time, he enjoys listening to music, playing Scrabble and birdwatching.

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