OK, so, let’s take the development of venom as a possibility. Venom could certainly make a jump in toxicity in a single evolutionary step. However, I would argue that going from “sort of venomous” to “really venomous” is unlikely to make a huge difference in the predator/prey relationship. In a situation like that, the prey’s main defense isn’t going to involve being resistant to the venom; it’ll be in avoiding the predator, through physical means (flight, speed) or behavioral (hiding). I can’t imagine a situation where those animals that get caught and envenomated, and then escape to survive another day, would make up a significant proportion of the population.
I believe what was happening was that the snakes venom would kill the bird but the snake that killed the bird would not reap the benefits. His posion had to be strong enough to stop the bird in its tracks. A snake cannot afford to waist protien rich venom. Most likley the birds would need to get faster reflexes because the snakes have become so successful and numerous that they are in virtually every bush. I see this relationship possibly collapsing in the future. My money would be on the birds winning this race.
From the point of view of the bird, though, it doesn’t make a difference whether or not it gets eaten. It’s still dead. So increasing the toxicity of the venom a notch or three isn’t going to suddenly drive the birds into extinction, which is the whole point of this thread.
Why qualify with “sudden”?
It’s implicit that … if. My question was whether.
Sperm whales and squid is an example that comes to mind. I believe there are also a lot of parasites who specialize in certain species.
But in general, the impact of the decline or possible extinction of a species is frequently described in terms of its impact on other species. So it’s not like others can just step in to fill the void and leave no impact.
There are also cases - as cited above - where the prey is the one with the venom. So being immune is crucial to the predator.
It would almost need to be sudden, otherwise the other species would have time to adapt.
But could we tell just from the fossil record that sperm whales and squid have such an exclusive relationship? Highly doubtful. Given the length of evolutionary time scales, the story would have to at least partially told in the fossil record.
Granted. I don’t see that that changes any of the conclusions made so far.
But that’s assuming that the other species is able to adapt given enough time. Suppose one species had genes which adapted faster, for whatever reason, then the other would slowly fall further and further behind over time.
I’m not sure what you’re saying here. I’m not saying anything should be documented in the fossil record. I’m merely citing sperm whales and squid as an example of species that have a close predator/prey relationship, such that if adaptations to one outstripped adaptations to the other it might impact the survival of the species. Whether such a thing could be documented is another issue entirely.
It relates to the specific point it was addressed to.
You were questioning whether venom resistance is all that big a deal, and I was observing that your point applied to the prey only and not to the predator. Because a predator would typically need venom resistance 100% of the time or close to it.
Suppose one species had genes which adapted faster, for whatever reason, then the other would slowly fall further and further behind over time.
Genes don’t adapt; they mutate randomly. Its the environment and ecology that determine if that mutation is an adaptation. The mutations keep on coming, regardless if they end up being adaptations.
If a faster rat comes along, it creates selection pressure for faster cats. Nobody wins because their “adaptations” are linked.
Well… I’m not sure this line of reasoning can stand up in all cases. For example, insects are largely limited in size because of limitations in their skeletal and circulatory systems. So let’s say that a beetle and a mouse are both experiencing selection for larger size. You’d have a short period where both can scale up using their existing organ structure (the “arms race”) but the beetle will quickly reach a maximum size. The beetle can’t scale up to rat size because it will suffocate without some novel new oxygen-exchange system. On the other hand, a mouse (under continuous selective pressure for size) can scale up quite nicely until you have a capybara (using another rodent as an example) or an elephant or whale (using other mammals as an example). There just aren’t any ten-ton beetles anywhere, ever, and there never will be until they reboot their skeletal and respiratory systems.
Relating this to the OP’s example, the selective pressure is going to happen pretty quickly (a few hundred generations, maybe; look at selective breeding in domestic animals). You get larger, larger, larger until you hit some limit in your environment or physiology that counters the selective pressure. Beetles DID lose the arms race for selection based on size, and so the ones that exist today fill niches where they compete on something other than size. Fossil evidence for that is going to be hard to find, as has been discussed.
All other things being equal, one expects organisms with a higher mutation rate to evolve faster (because there is more raw material to work with), and those with a shorter generation time to evolve faster as well (because there is more opportunity for selection to work). This said, trees are somehow able to keep pace evolutionarily with insects that eat them, even though the insects have a much shorter generation time.
It was my understanding that some creatures just tend to be more “flexible” in terms of genetic changes. A specific example I’ve always heard is dogs being more “plastic” as compared to cats; this being given as the reason there is more variation among types of dogs than among types of cats.
But are the trees keeping pace evolutionarily? I am aware that trees have defenses against insects, but what I’m wondering is if the primary factor that keeps tree species alive on an ongoing basis is these defenses, or the fact that so many predators prey on insects that their populations are kept in check, which gives the trees “breathing room” so to speak.
Smallpox? Humans were the “prey” species, the smallpox virus was the “predator”, and humans used technology, which is the characteristically human method of adaptation/evolution and wiped out the prey species.
Regards,
Shodan
Several people have suggested human examples. But I don’t know if these qualify. Humans have wiped out various species, but it’s not because humans have evolved faster than those species.
Humans are not fundamentally different than they were a couple of thousand years ago when those species flourished. It’s the cumulative nature of human learning rather than adaptive genetic change that is the factor here.
If they’re linked enough that the over-success of one could clearly be seen to be the cause of the extinction of the other, and it was the preditor species that over-succeeded, wouldn’t that send the predator species extinct as well? And even if Floobers only ever eat Flopsies and Flopsies are never eaten by anything other than Floobers, and one or the other go extinct; could we be sure that there wasn’t a disease or a parasite or a poisonous plant that either contributed or was the actual cause?
Given that we generally have little detailed information about species known only from fossils, the answer is we can’t really tell.
What about the smallpox variants that evolved to infect humans? I know humans are a bad example for almost every natural law, but if you think of virus as predator, and humans as the “prey”. The interaction provides a great example that’s accurately recorded.
Predator is initially dominant, and ravages prey population. Prey responds by “evolving” a treatment that protects an individual from the virus’ predation, and a system to spread that treatment throughout the entire species population. Predator dies out from lack of vulnerable prey until the only remaining survivors are samples stored by the prey.
See posts 31 and 32, dstarfire.
This sounds like the Red Queen hypothesis. And it has, indeed, been implicated in the extinction of some mammals, at least.
If you are limiting it only to genetic evolution, so be it.
The secret to the success of the human species is that we evolve culturally instead of only genetically. This is not only far faster, but more flexible. In that sense, humans have “won” the evolutionary arms race, because we have hit on a way to develop new “armaments” over a few hundred years instead of a few hundred generations.
Regards,
Shodan