Didn’t we cover this already? The Mullerian Two-Step explains this just fine: Which Irreducible Complexity Argument?.
It seems to me that “infection” is what bacteria do. So the event depicted in the article may not be as significant as the functional and behavioral aspect of the bee to flower symbiosis. Bacteria exist in our gut, so we have a symbiotic relationship with them. I can see how this would be akin to the activity described in the article. But if you look at the bee/flower relationship, there is a functional and behavioral relationship. Both aspects would have to evolve. Is that jump not significantly more complex to evolve than one bacteria infecting an amoeba example? Is it “fair” to look at the simple one and extrapolate such a complex symbiosis as the bees and flowers?
I think about a gall in an oak tree for instance. A wasp might sting the bark and the DNA is modified so that the bark grows into a soft gall. The wasp eggs are laid, the gall grows around it, the wasp flies off. The egg hatches, a larvae chews its way out and drops to the ground, it becomes an adult wasp, and the process is completed. In this case, the behavioral effect, which is beneficial to the wasp, is never realized (the parent doesn’t know that it was successful, the offspring doesn’t know how it was born) by the parent wasp. We have to simply trust that somehow, some way, this beneficial effect was inherited by the offspring and became inherent in the species.
Clearly there is no way that I can say that the same evolutionary effect that Joshua set forth above (steps 1-3) aren’t the same steps that were responsible for the relationship between the bee and the flower, or the wasp and the oak gall, but there seems to be a dramatic increase in complexity, which would require a dramatic increase in the number of adaptations, for these kinds of events vs. the infection of an amoeba by a bacteria.
(Please excuse any technical terms or details that were not stated correctly. I was merely trying to make a point about one seemingly simple example being an analogy for a very complex one.) I could be completely wrong about this, but it seems like a very simple explanation is being put forth for a very complex problem. When you look at this situation, do you find the simple example to be adequate to explain the more complex?
It is certainly not clear to me. Seems like it is fairly easy to see how symbiosis arises in this process. Infections become obligate endosymbiosis. Feed behavior by an insect becomes an obligate symbiosis by pollination for the plant, that benefits by producing more nectar to keep obliging insects alive. It is very easy to see both how this can arise, and also to see intermediate steps in this process.
It is possible that one of the plant biologists (@davecarlson or @art) might be able to give more concrete examples. As I understand it, plant evolution can be very rapid. It is possible that evolution symbiosis with pollinators is observable in the laboratory or in human observable timescales in the wild.
Thanks for the explanation, @swamidass!
One more thing, though, @swamidass, do you believe, then, that bees did not initially harvest pollen and manufacture honey? It seems, from the fossil evidence, that this is the case as soon as they came on to the scene.
I guess that the bees and flowers could both rapidly evolve such that the symbiotic relationship came about shortly after flowers and bees came onto the scene. Any insect experts on the board?
However, I do know you might broaden your notion of pollinator beyond bees. There are large range of pollinators. Anything that spreads pollen around is a pollinator.
Pollen might have first arisen for self-pollination in a structure that did not require a pollinator, and then evolve into grains that floated around in the air. With animals around, it would be easy to drift into a floral anatomy that required animals for self-pollination. Increasing the likelihood of pollination with nector is just a short step away. At that point, it is easy to imagine animals exploiting this for food, and becoming more and more obligated to symbiosis. Perhaps that is how bees arise.
I admit it is a just a hypothesis. It has to be tested, and likely already has been tested in the literature. It is just not my area, so I can’t say for sure. What we can see from this is a believable process by which symbiosis can arise by the mullerian two-step.
Thanks very much for this! Very interesting!
I’m pretty sure my grandma broke her ankle doing that, once.
So, it appears that pollen appears first at 240 million years ago, and the oldest bee fossil is about 100 million years ago.
Agreed. That’s what I had read also. I misspoke earlier. I had intended to suggest only that bees seemed to colonize in hives and make honey soon after their arrival. I was trying to find the article in which I read that, but I cannot locate it right now. Thanks for this, though!!
Given that the original post is from Dr. Rana at RTB, I’m curious what @AJRoberts thinks.
Great idea! Thanks very much!
Two really good papers on evolution of obligate pollination. Obligate mutualism is rare, and appears still to be observable in at least one case in human observable time scales in the wild. Notably, there is an evolutionary model that predicted the circumstances under which it would be more likely to take place, and this confirms these predictions.
Guys, I appreciate you wanting my opinion, truly. But I do not have time to defend and respond to questions that arise from posts that my colleagues make. Please continue to try and engage them directly. If you can’t get them to come here, I suggest you engage them where they are… on their Facebook pages is where most of their Q&A takes place. And if you can’t get a timely response to your queries, please realize they are involved in numerous projects and have to prioritize which critiques rise to priority. Their lack of response is not always because you have raised problems they cannot address scientifically. Please demonstrate some consideration in the way you treat their non-responses.
I very much agree.
The above response is in response to this thread… not in response to the thread on human chromosome fusion. Although the point I’m making here would be the same for that thread. But as you see, I took time to respond to that one b/c it rises to my threshold of interest and time.