Fig tree and Wasp Mutualism
Figs are pollinated by tiny wasps, too small for anyone over 30 to be able to focus on! Fig wasps pollinate a single species of fig. Fig wasp A pollinates Fig tree A, fig wasp B pollinates Fig tree B, you get the point…
This relationship is referred to as “obligate mutualism” and has been widely written about. From here on I’ll refer to this as “1 to 1”.
The “1 to 1” rule has exceptions. There are papers about hosts sharing pollinators and pollinators sharing hosts. There have also been studies of fig trees that grow over multiple countries having the same pollinator over their whole range. So what’s going on?
Firstly for the disclaimer: I’m not a fig wasp expert, I hardly know the difference between a flying ant and a wasp! Anything I say here is pure speculation, but that’s the beauty of a blog, I don’t have to prove anything!
Some thoughts on 1 to 1…
– Firstly fig wasps are hard to catch, they only emerge for a short time maybe only an hour or two per ripe fruit. The rest of the time they are either in the fruit or searching for a fruit to lay their eggs in. If something is hard to catch it’s probably hard to study.
– Not many people are able to identify fig wasps. You need a microscope to identifying them, so it’s highly specialised. This means only small quantities of wasp get identified.
– One tree could have millions of wasps on it, which makes identifying all of the wasps from one plant impossible. If there’s one dominate species of fig wasp, there’s a good chance none of the less common species will ever be collected.
– Like the figs they pollinate the fig wasps probably hybridise or are all so closely related that there are no true delimiters between the different species.
– I wonder if 1 to 1 is not so much a case of 1 species of wasp linked to 1 species of tree but more that one species of Fig is exposed to a new environment, it changes to suit it’s new environment and the same thing happens to the wasp. Both are exposed to a new environment and adapted as needed. In the case of the wasp it may not only be changing to suit climatically changes but also to the morphological changes of the fig’s flowers and ovaries.
– Darwin wrote about there being no true boundaries between species and of gradients of variation. The main difference between one species and another is the gap left between them when some of the intermediates die out. I feel that the current number of 800 species of fig trees is probably a lot more than the true number. With out knowing which trees are able to pollinate which other trees or which trees are just variations of other trees, we can’t really decide where one species begins and another ends.
– My final thought… 1 to 1 is a nice concept that probably doesn’t truly reflect the real world.