For as long as I can remember I have been fascinated by puzzles. Both those that you solve on paper, and those that involve fitting pieces together to create the complete picture. Perhaps this is why I am so drawn to the greatest jigsaw puzzle of them all – nature.
Everything in nature is interconnected, and even though some pieces might take us longer to slot into place than others, eventually the sum of the parts equals the whole. So often when we are out in the bush, in our haste to see as much as we can, we just look at the individual pieces. Whilst these are undoubtedly interesting, we sell ourselves short of a truly memorable experience if we do not pause for a minute to look around for more pieces to add to the puzzle, and the bigger picture.
Fig trees (Ficus spp.) are majestic trees found along rivers and watercourses throughout southern Africa. You may have taken shelter in their shade or even watched vervets and birds feasting on their ‘fruit’. I put the word fruit in inverted commas as it is actually a flower turned inside out! And herein lies a remarkable tale of closely interlocking pieces.
Wasps of the family Agaonidae have an extraordinary relationship with Fig trees. Each of the more than 750 species of Fig trees world-wide depends on these tiny wasps for survival. Coevolution has resulted in a few – but usually only one – species of these wasps being capable of pollinating the internal flowers of a particular fig species. The minute flowers of all fig trees are located in the hollow central chamber of the ‘fruit’, more correctly called the synconium. The entrance to this chamber is blocked by a closely interwoven network of tiny scales. The wasps have to negotiate their way through this obstacle course using spade-like heads to reach the flowers within. Like a lock and key mechanism, only a certain wasp species can negotiate its way through the entrance maze of each fig species.
Hereafter the picture becomes even more intriguing. Using chemical cues as a guide, a female fig wasp – with pollen stored in specialised receptacles on her body – migrates from the fig tree where she originated to another tree of the same species. Upon locating a suitable ‘fruit’ she wriggles her way through the maze, often losing wings and antennae in the process. Once inside, successful females deposit pollen onto the stigmas of some flowers and lay eggs in others. A protective gall then forms around the developing larvae. The wingless male wasps develop faster than females. Upon emerging, the males’ sense which galls contain the still-developing females and tunnel into the gall to inseminate them. The males then dig tunnels into the sides of the fruit that the females use to exit. The males then die. Once the females have emerged, they collect pollen from the fig cavity, make their way through the exit hole made by the males, and fly to another tree to repeat the process.
The nature of this relationship means that in any given area there must be at least one tree of the correct species, at the right stage of fruiting, and within flying distance of another tree from which the tiny, female wasps are emerging. Any disruption can result in local extinction of both species. This surely has to be the ultimate interlocking of two puzzle pieces.
I know what you are most likely thinking right now – probably with a slight sense of consternation: “I mean, do we really eat wasps when we eat figs?” The brief answer is that it depends! Some figs are parthenocarpic, meaning they are seedless. According to a 2006 Science study, these domesticated sterile figs could be evidence of the first use of horticulture in human history. The researchers discovered carbonised fig fruits in “an early Neolithic village, located in the Lower Jordan Valley, which dates to 11 400 to 11 200 years ago”. That’s nearly one thousand years before cereal domestication.
The commercially cultivated fig tree is usually a female parthenocarpic variety of the ancient common fig (Ficus carica) and does not need pollination to produce fruit. However, if whilst out in the bush you eat figs from wild growing trees, then it is possible that you are eating bits of wasp along with your snack. However, fear not! It is highly unlikely that you will know you are doing so since the fig produces an enzyme known as Ficin which breaks down the wasp into protein for absorption by the fruit. The final piece in a unique and complex work of nature.