Are there wasps in your snack?
Writer: Monika Yordanova
Editor: Sophie Maho
Artist: Iona Jenkins
Mmm, the taste of a perfectly ripe fig! Its flavour is quite unique and the sweetness of the fruit is subtle, and the juices it produces are so rich. It also has a special texture with a soft, supple outside, but the inside provides a divine crunch of seeds and… hang on, is that a wasp? Wait… what?
Yes, you read that right. It’s time for you to find out about the secret life of a fig wasp and its mutualistic relationship with figs. Brace yourself, because this small insect’s life cycle is dependent on violence, incest and betrayal to a degree not even Game of Thrones could compare to.
Let’s start with their hosts. Figs are no conventional fruit. Before our friends, the fig wasps, even get to them a fig actually resembles a small garden with a huge number of flowers all tucked into a neat little pouch. This is known as an inflorescence. This inflorescence, however, is quite selective about who it allows to pollinate it. The synconia, where all the flowers grow, is impossible to get to until the fig reaches maturity. Once it does, it allures the female fig wasp, with its sweet scent. The wasp certainly is enticed by this aroma. In fact, even when entirely reliant on her sense of smell, female wasps are still able to reach their targets. Furthermore, despite their short life cycles of about 2 days, and the fact that their body is smaller than the head of a needle, these wasps have been reported to travel up to 10km to reach their hosts.
The female wasp arrives at her host. But her adventure has only just begun. Her incredibly small size comes in handy as she climbs inside the fig’s tiny hole, known as an ostiole, which is found at its base. The hole is covered in tight turgid scales that protect the fig from unwanted intruders. Unfortunately, it also prevents the entry of our friendly fig wasps. The wasp struggles and pushes through to enter the fig’s sweet gardens. Often this is done at the cost of losing her own wings and sometimes even limbs in the process.
Once inside something weird happens. The wasp lays her eggs inside some of the female flowers. In the process, she also pollinates other female flowers. This is exceptional in some species as they actively ensure this process by collecting pollen in specialised pockets via combs found on their legs. They then purposefully deposit this pollen into the female flowers. This active collection and deposition is extremely rare among pollinators; besides fig wasps, it has only ever been observed between yucca plants and yucca moths as well as in senita cacti and senita moths. It seems wasps have a lot of dedication to help their friendly nannies, the figs. Once her reproductive role is completed and she has ensured the next generation of both herself and her host, the female wasp dies from exhaustion.
Her sons emerge first. They are wingless and small-eyed, and their body is minute compared to their sisters. They do however have large penises and giant mandibles to help them fight off potential competition. Not all species will fight; in fact, some are peaceful. But in many species, the males will bite off their rivals’ heads to increase their own reproductive success. While these savages are fighting, the females are still blissfully asleep in their gulls happily feeding, but their slumber is soon disrupted by the aforementioned large penises that reach them from the outside of their galls. Now you may be thinking this seems wrong. It gets worse. You may remember that some of them are also their sisters. Um, I guess they really love their family…?
The males then gallantly chew a way out for their mates to allow them to exit the figs when ready. The females emerge into the synconia just as the male flowers of the fig do too. They fill up their pollen sacks and leave ready to restart the incestuous violent cycle anew.
Eww, so does that mean that every time I bite into a fig I am eating wasps as well? Well, not quite. There is a wide variety of figs and although most rely on wasps for pollination, not all of them rely on pollination to the same degree. In a monoecious fig, both female and male flowers are found in the same fruits as just described, but there are also dioecious figs. These have separate male and female fruits. It these cases, male fruits produce florets, where wasps can deposit their eggs. The younglings that emerge from them can then serve as vectors to carry their pollen. In dioecious figs, the female fruits look identical to the male ones, therefore, just by chance, one of the hundreds of wasp offspring is bound to get tricked by a female fig and lured inside. There, the wasp cannot lay her eggs and simply serves to pollinate this fig. She then dies alone, exhausted and childless, despite all of her trials and tribulations that she has endured. But this ensures that the figs will produce seeds giving rise to its next generation of figs and by extension wasps. Therefore, the life cycle of these figs is dependent on betraying of their mutualists.
An example of such a fig variety is the common commercially available variety, Smyrna. We eat the female figs, which produce seeds, and enjoy their crunchy taste. Don’t worry, the female wasps become metabolised by the fig anyway, so the crunch is not produced by the bodies of dead wasps. Furthermore, some figs varieties like Brown Turkey do not even require wasps at all as they do not require pollination. Of course, humans have ensured the success of these varieties, as they would not have been adaptable enough to be successful on their own.
Regardless of whether this has reassured or dissuaded you from ever eating figs again, one thing is certainly clear: figs and their pollinators are hardcore and the fig’s relentless dominance over its persistent pollinator call for us to re-examine how friendly mutualisms are. Hopefully, it has also shown you that despite the mistreatment of fig wasps by dioecious figs, their mutualistic relationship has become dependent on some degree of exploitation for its evolutionary stability. Similar to how some of these male wasps have become dependent on killing some of their brothers. Despite the fact that this reduces their indirect fitness, wasps will continue this fight to ensure their own survival and reproduction and ultimately this helps them continue their species’ success. Most importantly, however, I hope that from this story of figs and their magnificent pollinators you’ve now had a glimpse into the gory mechanisms nature uses to create the beauty and perfection that we admire and appreciate. Crunch!
Sources
Cook, James M. & Jean-Yves Rasplus. (2003) Mutualists with Attitude: Coevolving Fig Wasps and Figs. Trends in Ecology & Evolution 18(5): 241–248.
Galil, J. (1977) Fig Biology. Endeavour 1(2): 52–56.
Gibernau, M., Hossaert-McKay, M., Frey, J. E., Kjellberg, F. (1998) Are olfactory signals sufficient to attract fig pollinators? Ecoscience 5(3):306-311
Piedra-Malagón, E. M., Sosa, V. & Ibarra-Manríquez, G. (2011) Clinal Variation and Species Boundaries in the Ficus Petiolaris Complex (Moraceae). Systematic Botany 36(1): 80–87.
Proffit, M. & S. D. Johnson. „Specificity of the Signal Emitted by Figs to Attract Their Pollinating Wasps: Comparison of Volatile Organic Compounds Emitted by Receptive Syconia of Ficus Sur and F. Sycomorus in Southern Africa. South African Journal of Botany, 75(4): 771–777.
Raman, A., Schaefer, C. W. & Withers, T. M. (2005) Biology, Ecology, and Evolution of Gall-Inducing Arthropods. Enfield, Science Publishers, Inc.
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