In the not too remote past, considering the enormous antiquity of our world, a group of animals wanted to eat. They were carnivores, so they needed to hunt other animals for food . And they did it on the run. Of course, when a predator appeared, the entire herd of prey would run in panic. And generally, slower prey got more ballots in the evolutionary raffle . The fastest prey managed to survive longer, and therefore, have more offspring, which also inherited their greater speed.
But that turned out to be a problem for predators. By hunting the slow prey, only the fastest ones were left, so not everyone got their prey. The slower predators did not get as much food, and that led them to die more easily. However, the faster hunters still managed to catch some prey, and thus survive longer and have more offspring to inherit their greater speed.
This generated a new pressure on the prey, so that only those that managed to be faster than the new and improved predators managed to survive. And that generated, again, pressure on those predators. A kind of race to reach the highest speed, which to this day, gazelles and cheetahs continue to maintain . We call this type of race, in evolutionary biology, the red queen. A parallel evolution maintained by predator and prey, in a constant pulse in which each side produces greater —selective— pressure, and whose final result is the maintenance of the status quo .
A race millions of years old
This dynamic is not new. Its origin is as old as the very origin of predation. Since, during the evolutionary radiation of the Cambrian, there began to be animals capable of hunting other animals, the fittest predator has generally been the one that best hunts its prey; while the fittest prey tends to be the best defended against predators . Predators have needed to offset defensive improvements in prey with offensive improvements; while the prey increase their defenses to protect themselves from the increasingly better attacks of their predators.
A new jaw shape capable of tearing flesh, and an exoskeleton capable of withstanding such attacks. A better camouflage that prevents being detected by sight, and a better sense of smell that allows detecting hidden prey. A frontal orientation of the eyes that allows calculating the distance at which the prey is located; and a lateral orientation of the eyes that allows monitoring more extensions of land. A better hearing, coupled with the ability to orient their ears; and a new pad system that reduces noise when walking. Novel systems that are polished during the evolutionary process, in a constant selective pressure of the predator over the prey, and of the prey over the predator. An arms race over 500 million years old, still going on today.
other red queens
And this race is not only found in the dynamics of the predator and the prey. Let us think of a pathogenic virus, which infects a population . Those individuals most susceptible to the disease will have fewer chances, and those most resistant to the virus will be those that survive better and leave offspring with greater probability; but only those variants of the virus capable of infecting the most resistant individuals will survive over time. And in the end, the status quo remains
Or think of a parasite ; the host with the best immune system will be able to better withstand the parasite; but in return, those parasites capable of staying in their hosts, however resistant they may be, will be the most suitable. The parasite presses on the host, and the host presses on the parasite. And in the race it is possible, finally, to maintain the status quo.
However, not all of those relationships have to be negative. The red queen also happens in mutualism relationships in which both parties benefit. One of the most beautiful examples is that of the famous hawk moth, Xanthopan praedicta , so called because Charles Darwin and Alfred R. Wallace themselves predicted its existence without even knowing it, thanks to their understanding of the evolutionary process and the discovery of the strange flower it pollinates.
Let’s tell the story from the beginning. A flower that is pollinated by a moth. To attract the moth, the flower produces nectar at the bottom of an inverted conical structure that we call a nectary. The moth feeds on that nectar, but getting too close to the flowers damages the moth’s wings . The most suitable moth is, therefore, the one with the longest tongue, which allows it to sip nectar without suffering damage. However, this produces a selective pressure on the flowers; if the moth does not get close enough, the pollen does not stick to its body and there is no pollination. Those that have the deepest nectary therefore force the moths to get closer, and they pollinate better. The flower presses down on the moth as it feeds it, the moth presses down on the flower as it helps it reproduce. They both push, and they both win. The result: flowers with a 30 cm deep nectary and moths with a 30 cm long tongue. And the status quo is maintained.
Why “the red queen”?
“Well, what it is in my country,” Alicia clarified, still panting heavily, “when you run as fast as we’ve been doing and for some time, you usually end up somewhere else…
“A pretty slow country!” replied the Queen. What it is here, as you can see, you have to run as much as you can to stay in the same place. If you want to get somewhere else you have to run at least twice as fast.
Lewis Carroll, Alice Through the Looking Glass
Hypothesis of the Red Queen, this is how the researcher Van Valen called this striking process, which finds a perfect analogy in Alice’s conversation with the Queen. The overall process can be summed up in a single visual image: a constantly and inexorably moving scenario, in which species must be constantly evolving, running alongside each other without stopping, just to maintain the status quo.
REFERENCES:
Clarke, D. K., Duarte, E. A., et al. 1994. The red queen reigns in the kingdom of RNA viruses. Proceedings of the National Academy of Sciences, 91(11), 4821-4824. DOI: 10.1073/pnas.91.11.4821
Liow, L. H., Van Valen, L., et al. 2011. Red Queen: from populations to taxa and communities. Trends in Ecology & Evolution, 26(7), 349-358. DOI: 10.1016/j.tree.2011.03.016
Morran, LT, Schmidt, OG, et al. 2011. Running with the Red Queen :
Host-Parasite Coevolution Selects for Biparental Sex. Science, 333(6039), 216-218. DOI: 10.1126/science.1206360
Van Valen, L. 1973. A new evolutionary law. Evolutionary Theory, 1, 1-30.
