Coevolution is when groups of animals undergo reciprocal evolutionary changes. An evolutionary arms race occurs when two animals continually out-evolve each other in order to maintain the current state of affairs, such as prey evolving to outrun predators.
When we hear the phrase “call to arms,” we usually don’t think of bats chasing insects. Guns, cannons, tanks… sure, but bats and moths? Not so much.
However, bats and moths are actually engaged in a war with each other. They have a closely intertwined relationship, the short version of which is that the bat population (predator) hunts down the moth population (prey). However, there’s much more to this interaction than meets the eye.
The battle first began when bats evolved the ability to use echolocation to detect moths in the dark. The bats would emit high-frequency sounds or pulses from their mouths or noses and then listen for the echo that returned.
Bats use their snouts to detect the echoes. (Photo Credit : D. Kucharski K. Kucharska/Shutterstock)
The bats had gained an evolutionary advantage. In response, the moths developed a clever response. They evolved ears that allowed them to hear when a bat used echolocation!
Bats Vs. Moths: Defining an Evolutionary Arms Race
Bats use echolocation at frequencies between 20-50 kHz. Moths also hear best at frequencies around 50 kHz. Coincidence? Definitely not.
Moths also evolved the ability to produce ultrasonic clicking pulses. Essentially, they can use these clicks to startle bats using echolocation. When the bats emit their own sounds or pulses, the moths produce their own clicks. These clicks interfere with the bats’ ability to locate their prey.
And the battle continues like a tennis match. In response to the moths’ countermeasure, bats adapt by using echolocation at different frequencies, ones that moths can’t hear. For example, spotted bats in North America use incredibly low frequencies of 12 kHz.
Some bats have taken a completely different approach. The short-eared trident bat in Africa uses a super high-frequency 208 kHz call for its echolocation needs!
This ongoing series of interactions and adaptations is known as an evolutionary arms race.
So, while most of us associate an arms race with hostile nations stockpiling weapons of mass destruction to oppress and antagonize each other, there is another type of arms race that is equally fascinating to learn about!
Articles with bolded words like these are usually associated with arms races. (Photo Credit : frank333/Shutterstock)
It’s not just these two species that have been locked in this type of battle for countless generations. Many animals find themselves in similar struggles. It’s a perpetual battle with no end in sight. The battle they are fighting is the battle for survival and outsmarting each other. It’s the battle of coevolution.
Evolutionary Arms Race and Coevolution
Coevolution refers to the phenomenon of reciprocal evolutionary changes between groups of animals. Essentially, it’s a give-and-take situation.
Take, for instance, a herd of impalas on the savannah. They are nimble and can outmaneuver their primary predators, cheetahs. In response, the cheetahs have evolved to match or surpass the speed of their prey. These swift cheetahs hunt down impalas that are slower than them. Only the fastest impalas survive, passing on their speed genes to their offspring. This creates an evolutionary arms race driven by the coevolution of these species.
Faster impalas are able to avoid predators and produce offspring that inherit their speed. This is an example of sexual selection. (Photo Credit: Anan Kaewkhammul/Shutterstock)
There are various theories, such as the geographic mosaic theory of coevolution, that attempt to explain the origins of coevolutionary interactions. The first documented example of coevolution was provided by Darwin himself. In his book On the Origin of Species, he described the mutually beneficial interactions between flowering plants and insects.
What Are The Different Types Of Coevolutionary Interactions?
Coevolution does not always involve antagonistic interactions between two animals. There are also mutualistic examples of coevolution, such as plant-pollinator interactions. Angraecum sesquipedale, an orchid species, can only be pollinated by a specific type of hawkmoth. This is because the hawkmoth possesses a long proboscis that allows it to access the orchid’s nectar spur. This interaction is mutually beneficial as the plant gets pollinated and the moth obtains nectar rewards. (Photo Credit: Lisaveta/Shutterstock)
While antagonistic interactions between prey and predators or parasites and hosts are the most common examples of coevolution, it is interesting to note that antagonistic interactions can also occur within the same species.
Consider bees, for instance. Bees living in large colonies have well-defined roles and a hierarchical structure consisting of queens, workers, and drones. Pheromones mediate most interactions within a bee hive. The queen bee produces a pheromone that inhibits the reproductive abilities of worker bees, rendering them sterile. Worker bees continuously evolve to overcome this inhibition, either by developing immunity or insensitivity to the queen bee’s pheromone.
The queen bee and the worker bees engage in an ongoing evolutionary arms race, but it is not purely antagonistic as it serves to maintain the hive’s status quo.
What Influences The Coevolution Of Species?
Several factors influence coevolution, with the most significant being selection pressure. Selection pressures encompass external conditions or factors that affect the fitness (evolutionary fitness) of an organism. These pressures can be negative, such as floods or an increase in predator population, or positive, such as when a parasite decimates a dominant predator population.
Conclusion
Coevolution, like other evolutionary mechanisms, can be disrupted by human interference, but it can also be harnessed for beneficial purposes. For example, consider the arms race between bacteria and antibiotics. When Alexander Fleming discovered penicillin, the world’s first antibiotic, it was hailed as a miraculous drug capable of combating bacterial infections.
Bacterial strains have the ability to become resistant to antibiotics, which has led to further research in the development of new drugs. (Photo Credit : Jarun Ontakrai/Shutterstock)
However, it was not anticipated that bacterial species would develop specific resistance to the antibiotics that are used to treat them. This is why a significant amount of money is invested in pharmaceutical research and development every year. We actively work on creating drugs that can combat bacterial resistance, but the bacteria continue to develop resistance to each new drug that is developed.
Fortunately, there are also positive examples of coevolution between humans and other species. One such example is the domestication of dogs by humans. As the domestication process progressed, dogs learned to adapt and serve human interests better, even as their lifespan increased and their species became more diverse. This has resulted in a mutually beneficial relationship between the two species!