You may have once come in contact with this concept: “adaptive radiation” , widely used in evolutionary biology. Adaptive radiation, as its name suggests, is an adaptive biological process in which certain species can fill an ecological niche very quickly.
This phenomenon of domination of the territory by certain species is known as “speciation” and is part of an evolutionary process, since mutations and aspects of natural selection are involved.
In this article we will see in detail what these concepts consist of; ecological niche, mutation and natural selection, fundamental concepts to understand what adaptive radiation is. And finally we will know what adaptive radiation is, what are its causes and origins, characteristics that determine if we are in a situation of adaptive radiation, types of adaptive radiation and some examples.
What is adaptive radiation?
As we have introduced previously, adaptive radiation arises from a species adaptive issue. It is very common for this phenomenon to appear in an ecosystem where a new species is introduced, or when there are already species in that ecosystem that manage to survive in that environment that they had not managed to do so before.
In this process, the appearance of genetic mutations is necessary . A genetic mutation is a change in the genetic material that makes a phenotypic change possible, that is, in the expression of that characteristic in the organism of that animal. Such mutations can give them characteristics that are favourable to their survival, or negative.
Therefore, it is normal that if this (random) mutation that occurs in the animal provides it with some capabilities that allow it to adapt better to the environment, this group of animals with this mutation survive more and pass this mutation to their descendants , and that those that do not adapt (without the mutation), end up disappearing.
This is where the concept of natural selection comes from; Darwin, the scientist who postulated this concept, defined that natural selection establishes that the conditions of an environment or ecosystem favour or harm, that is, they select, the reproduction of living organisms according to their characteristics.
In other words, if in a giraffe ecosystem where the trees with food are very tall, and thus only giraffes with very long necks have access to food, those with a mutation in their genetic material that gives them a longer neck, will survive longer because they will feed more and not starve.
And so these giraffes, not dying, will be able to have offspring, and it is very likely that their descendants will inherit such a mutation. Little by little the giraffes that do not have characteristics to eat and not die of hunger, will die, and of course they will not be able to pass on their genetic material. These species then fill what are known as ecological niches , which are understood as the functions performed by the species within an ecosystem.
Characteristics of this biological phenomenon
There are a series of characteristics that allow us to define an adaptive radiation process, they are the following.
1. A common ancestor
One of the fundamental characteristics of adaptive radiation is that all species that are derived have a single common ancestor .
2. Phenotype-environment correlation
The existence of a correlation between the phenotype (the characteristics that are manifested in the organism) and the environment is essential to talk about adaptive adaptation. That is, that there is a significant relationship between the morphological and physiological characteristics of the organism and the environment.
3. Utility character
That is, that the morphological and physiological characteristics of the organism are adapted to the needs of the environment . That is, that these characteristics are useful to the animal for its survival.
4. Speed in the process
Let speciation be a response to the need to adapt to the environment, and be a quick process.
Types of adaptive radiation
There are basically three types of adaptive radiation known .
1. General adaptation
This type of adaptive radiation occurs when a species develops a radically new characteristic or ability that can lead to the invasion of new parts of that environment . An example of this would be the flight of certain species of birds that facilitates their arrival in other spaces.
2. Environmental change
In this case, a species that has the capacity to survive in a radically changed environment , compared to others that do not have that capacity, is very likely to branch out into new species, covering other ecological niches.
An example of adaptive radiation in response to environmental change would be the rapid expansion and development of mammals with the previous extinction of dinosaurs.
This type of adaptive radiation focuses on archipelagos, which would be isolated ecosystems such as islands or mountainous areas .
These can be colonized by new species which, if established, follow a rapid process of evolution in which they diversify. The clearest example would be Darwin’s finches, which we will see below.
Examples of adaptive radiation
Real and documented examples of adaptive radiation would be, for example, Darwin’s finches from the Galapagos Islands. Darwin’s finches were birds that developed and reproduced from a single species of finch that arrived on those islands at a certain time.
In this case, there was a diversity of beaks in the different species of finches. These finches were derived from the same ancestral species, but had been adapted to different ways of feeding, hence their beak-shaped varieties.
Other documented cases of adaptive radiation include the introduction by man of predatory mammals into certain regions of Australia , with their survival and expansion, or the development of dipnoids (fish with lungs) over a period of time that took place around 300 million years ago.
In all these cases, there are certain common factors that qualify them as examples of adaptive radiation: genetic mutations that lead to phenotypical changes, better adaptation to the environment than other species in the same ecosystem, and finally rapid colonization of that species in that ecological niche.
- Carranza, J. (2016). Adaptive ethology: behavior as a product of natural selection. UCOPress, Editorial Universidad de Córdoba, 1st Edition.
- Gould Stephen, J. (2004). The structure of the theory of evolution. TusQuets Editors.
- Pincheira-Donoso, D. (2012). Adaptive selection and evolution: Theoretical and empirical foundations from the perspective of lizards. Ediciones UC.