The concept of coevolution comes from the Darwinian concept of evolution. It can be defined as the situation where the evolution of multiple species is affected by the actions of another species cohabiting in the same ecosystem.
In simple terms, coevolution occurs when two species end up affecting each other’s evolution.
This occurs because evolution can occur in reaction to changes in an organism’s environment. So, if an ecosystem changes, all animals in that ecosystem may co-evolve in reaction to the changes in the environment.
Organisms with symbiotic relationships are often found to evolve in tandem with each other. This happens as one organism needs to adapt itself to keep up with the modifications and evolutions of the other species.
The relationship between multiple organisms can be beneficial for both or one of them. They even can be in a competitive relationship where they compete with each other to survive in that ecosystem.
Types of Coevolution
Coevolution can be of multiple types:
- Pairwise coevolution (Specific coevolution) – When coevolution occurs between two specific interacting species.
- Diffuse coevolution (Guild coevolution) – When multiple species in an ecosystem evolve together in reaction to an environmental change.
- Gene-for-gene coevolution (Matching gene coevolution) – When two species’ genes evolve in unison. This usually occurs in parasitic relationships.
Coevolution Examples in Nature
1. Snail Shell and Crab Claws
Type: Pairwise coevolution
A strong connection exists between the increasing thickness of snail shells and the strength of crab claws over time.
As crab claws started getting thicker to improve their ability to prey on snails, snails also started increasing the thickness of their shells to protect themselves from the crabs’ shaper claws.
This is a classic example of coevolution where both organisms evolved in a way that will favor them better to survive in their respective habitats.
Related Article: 15 Intraspecific Competition Examples
2. Flowering Plants and Pollinators
Type: Diffuse coevolution
Pollination is an important aspect of the lifecycle of flowers. Organisms like birds and insects play a major role in carrying off and distributing flowers’ pollen to distant places.
Once the insects or birds feed on the flower nectar, the flowers obtain the chance to deposit their pollen onto these organisms. When the birds and insects visit another flower right after feeding onto the pollinating flower, they will end up transferring pollen between flowers.
In this relationship, flowers get their pollen carried to different plants, while the birds and insects benefit from the supply of nectar from the flowers.
At times, these flowers also often act as nests for the insects where they further lay egg. Ehen these young insects fly out into the world they further carry the pollens with them.
To gain evolutionary advantage, some flowers often have developed traits that lure their target pollinators towards them. This includes developing colorful, vibrant-looking flowers for gaining the attention of animals with color vision.
Similarly, some flowers have evolved to be extra sweet to attract insects and birds.
3. Birds and Plant Fruits
Type: Diffuse coevolution
All kinds of birds, but particularly the ones involved in fruit consumption, are directly involved in a symbiotic relationship with plants and hence show signs of ongoing coevolution.
Birds feed on the fruits of plants to fulfill their appetite. The majority of the plant seeds present in the fruit of these plants have evolved to be digestion-resistant.
This means that birds will discharge full seeds out of their body. These get dispersed to different locations and possesses the capability of growing up into a new tree. The birds discharge the seeds not only through the process of stool discharge but also through regurgitation.
Interestingly, fruit trees have evolved differently depending on the types of birds in their ecosystems:
- Plants growing around bird species that can spot color have vibrantly colorful fruits.
- In ecosystems where birds are mostly color blind, fruits tend not to be so colorful. However, those fruits have a strong scent that equally does the job of attracting the birds.
Read Also: 15 Commensalism Examples
4. Coral and Sea Sponges
Type: Pairwise coevolution
Coral and sponges demonstrate a competitive symbiotic relationship that forces them to coevolve together.
Competition exists between the coral and sponges where each aims to dominate the vast stretches of the ocean floor.
To keep up with the competition both need to adapt and evolve at a constant pace. If any one of the two gets ahead of the other, it can lead to their destruction in the ecosystem.
This can then have catastrophic results as both the sponges and corals depend on each other for their survival and are important for maintaining a balance in the ocean ecosystem.
Sponges need the coral because it acts as a strong anchor to keep the coral from floating away. The sponges entrap the excess amount of nutrients present in the adjacent water and then further distribute it through the coral reef. They also attract and entrap many different kinds of algae and microbes which further allows the sponges and corals to form symbiotic relationships with these organisms.
5. Bats and Pitcher Plants
Type: Pairwise coevolution
Bats and pitcher plants exhibit a fascinating mutualistic relationship with each other. The pitcher plants provide the bats with a safe roosting location where they can rest safely without the fear of facing any sudden danger.
This relationship is shown to be exhibited by Kerivoula hardwickii bat species and the Nepenthes hemsleyana pitcher plant species.
The pitcher plant does not harm the bats in any way even though they are fully capable of consuming them. This is because, in exchange for providing a safe resting place to the bats, the plants benefit from the bat discharges within the pitcher plant.
Bat poop is stuffed with nitrogen and a variety of other minerals and nutrients which the plant has a serious deficiency.
6. Herbivores and Plants
Type: Diffuse coevolution
Herbivores are animals that only eat plants as their primary and only food item. Throughout evolution, they have undergone many physical adaptations that make the process of eating and digesting plants more favorable than other organisms that are omnivorous.
Herbivorous animals have wide molars which help them to grab and chew leaves and other plant portions in a better way. Omnivorous and carnivorous animals on the other hand much sharper teeth which will help them to tear through flesh.
They have specialized enzymes in their stomach that help them better digest the cellulose present in plants.
They also contain particular kinds of microbial flora in their gut that help in further breaking down these food items better.
7. Fig Trees and Fig Wasps
Type: Pairwise coevolution
This is another example of mutually beneficial coevolution. Female fig wasps belonging to the Agaonidae family burrow their way into the flowers of fig trees.
Female wasps lay their eggs within the flowers. Then, and after the oviposition (once the offspring are born), they end up feeding on the internal tissues of the fig plant.
Males also live off the fig trees. They chew their way around the trees and produce holes or tunnels through which female wasps fly away to different locations to start their own families.
Male wasps often end up spending their lives in the same tree where they are born. The female wasps, while flying away to different locations, carry the pollen fig plants with them, thereby allowing fig trees to reproduce.
This whole process is very particular in nature. Each species of the wasp only lays its eggs in one particular species of the fig tree. This ensures that the pollen from one particular fig tree species goes to a distantly located fig tree of the same species.
This interdependence is of immense importance to both the wasps and the plant. This is something that has evolved over thousands if not millions of years and as a result, both of them have coevolved in a way that will enhance their association.
8. Scarlet King Snakes and Coral Snakes
Type: Pairwise coevolution
This is a classic example of coevolutionary commensalism. Here in this example, the association is based on Batesian mimicry. In such instances, one organism mimics another more dangerous organism. This further enhances their defense systems and enhances their chances of survival.
Relatively harmless scarlet kingsnakes mimic some features of harmful coral snakes which allows them to gain a competitive advantage in the wild.
They bear the same kind of body coloration and banding as the poisonous coral snakes. This only happened as they coevolved at the same location over many years.
Other animals fear them, even though they don’t have to.
Mimicry helps the kingsnakes immensely as coral snakes are considered highly poisonous and dangerous snakes which can inflict serious damage to their predators. So, the majority of the potential predators of kingsnakes in the wild avoid crossing paths with kingsnakes in case they are actually coral snakes.
Scarlet kingsnakes are nowhere near as dangerous as coral snakes and in fact they are considered quite harmless. But by mimicking the physical traits of the coral snakes, they have enhanced the chances of their survival by many times.
9. Myxoma Virus and Australian Rabbits
Type: Pairwise coevolution
This is an example of host and parasite coevolution where the parasite evolves in a way along with the host that further helps them to adapt to the host’s body system and defenses.
The host on the other hand keeps on evolving its defense systems in the body to get rid of the parasite.
In Australia, there was an overabundance of rabbits in the middle of the 20th century. So in the 1950s, the maxima virus was used to regulate the rabbit population in Australia.
Initially, the maxima virus was successful in controlling the rabbit numbers and halted their growth. The population got reduced from 600 million to 100 million—the majority of the rabbits that got infected died within a few weeks.
But with time the rabbits were found to undergo genetic changes that allowed their body defense system to tackle the virus with suitable ease.
So, the plan that was initially working flopped because the rabbits started to adapt and evolve in a way that makes them resistant to the threat of this particular virus.
This mainly occurred as many rabbits which managed to survive after contracting the initial infection reproduced and passed on their genetic protection to their offspring.
With each generation hereon, more and more genetic variations started to happen which allowed the next generation of rabbits to overcome the lethal effects of the virus.
10. Wolves and Caribou
Type: Pairwise coevolution
Wolves are the predator and caribous are the prey. Wolves are fast movers and hence only the fastest and fittest of the caribous will be able to evade predation by wolves.
The strongest caribous who survive will be able to pass on their strong genes to the next generation. Because of this constant threat from their predators, the remaining population of caribous evolves to be extra fast and strong.
On the other hand, as caribous are getting faster, so too are wolves. The wolves need to get faster otherwise they won’t be able to survive. So, only the fastest of the wolves will be able to hunt for the fast-moving caribous, and these wolves will have a better chance of survival and reproduction than the slow-moving wolves.
So, both the caribous and wolves influence the evolution of each other through their presence in the same ecosystem.
Conclusion
Coevolution is one of the reasons why animals have grown from small multicellular organisms to the complex species of today. Over time, species have become stronger, fitter, and smarter in order to more effectively hunt and avoid predation. Similarly, many plants have even evolved to have sweet smells to attract animals that can help them pollinate and reproduce, while animals like hummingbirds have developed long straw-like beaks to suck up the pollen.
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