Introduction to Parallel Evolution
Introduction
Parallel evolution is the type of evolution when two types of species evolve together and starts acquiring the same characteristics as each other at the same time.
These groups of species are geographically separated but they have the same morphological resemblances.
Introduction to Types of Evolution
There are three distinct types of evolutions: Divergent, Parallel and Convergent.
In convergent evolution, similar types of traits start evolving independently of each other. Homologous structures are formed from convergent evolution.
Divergent evolution occurs when two populations are separated by a geographical barrier and are subjected to divergent selective forces that promote adaptations to their new habitat.
Parallel evolution happens when two distinct species evolve in the same direction and so acquire identical characteristics independently, for example, gliding frogs evolved in parallel from several different types of tree frogs. Convergent evolution in plants can be shown in the development of C4 photosynthesis, and seed dispersal via fleshy fruits meant for animal consumption and carnivory
Characteristics of Parallel Evolution Theory
If the ancestors shared that resemblance, the evolution of that character in those species is characterised as parallel; if they did not, the development of that character in those species is said to be convergent. Parallel evolution and convergent evolution, according to some biologists, are nearly indistinguishable.
The distinction between parallel and convergent evolution becomes more subjective when the ancestral forms are unidentified or unknown, or when the range of features evaluated is not specified. The apparent similarity between placental and marsupial forms, for example, is the result of convergent evolution.
Example of Parallel Evolution
Some very common examples of parallel evolution include:
Many diverse species have evolved colouration that serves as a warning to predators and for mating displays.
The most well-known instances of parallel evolution in the plant kingdom are leaf shapes, which have evolved repeatedly in different genera and families with extremely similar patterns.
It has been proposed that populations of Arabidopsis thaliana adapt to the local environment through parallel evolution.
The patterns of wing colouration in butterflies are strikingly similar, both within and between groups.
Parallel Evolution Between Marsupials and Placentals
The two main lineages of mammals, placentals and marsupials, have followed separate evolutionary paths following the break-up of landmasses such as Gondwanaland around 100 million years ago, and give many examples of parallel evolution. Before the Great American Interchange, marsupials and placentals shared the same ecology in South America, marsupials won in Australia, while placentals won in North America.
However, until the cataclysmic extinction of dinosaurs 65 million years ago, mammals were small and occupied just a small portion of the environment in all of these locations. Mammals on all three continents began to take on a far broader range of shapes and functions. While certain animals were unique to each environment, comparable animals frequently appeared on two or three of the continents that were separated. The placental sabre-toothed cats (Machairodontinae) and the South American marsupial sabre-tooth (Thylacosmilus) are examples, as are the Tasmanian and European wolves, as well as marsupial and placental moles, flying squirrels, and mice.
Genetic Role in Parallel Evolution
The first factor is a similarity between organisms. Jellyfish and anemones have a radial body layout, which means they don't have a left or right side. However, a signature for a bilateral body design has been discovered in their genetic coding. It doesn't appear to be expressed in jellyfish for some reason.
The experimental evidence is the second factor to consider. Parallel evolution has recently been studied by biologists who have gone beyond morphology. They discovered evidence that physical similarities were matched by genetic similarities in at least some cases. In two species that had been separated for millions of years, the chemical interactions of proteins and amino acids that induce morphological changes were also the same.
Conclusion
It is very well clear that evolution is a complex process. Hence, there are several factors that aid or cause the changes occurring in the process of evolution. The theory of parallel evolution plays a significant role in the explanation of the development of organisms and species as a whole along with other theories of divergent and convergent evolution. Of all of them, parallel evolution best explains why some species that have been distinctly related to each other over generations share certain similar characteristics in phenotypes and/or genotypes that could have come from a single ancestral source.
FAQs on Parallel Evolution: What Does it Entail?
1. What is the fundamental concept of parallel evolution?
Parallel evolution describes a process where two or more distinct species, which have a common ancestor, evolve similar traits independently while occupying similar ecological niches. This happens because they are subjected to similar environmental pressures. The key aspect is that they start from a similar ancestral point and evolve in a parallel direction, rather than converging from very different starting points.
2. What are some key examples of parallel evolution in animals?
A classic example of parallel evolution is seen between placental mammals and Australian marsupials. After the continents separated, these two groups evolved independently but developed remarkably similar forms to fill corresponding ecological roles. For instance, the placental wolf and the marsupial Tasmanian wolf (thylacine) both evolved to be large, dog-like predators. Another example includes the parallel development of long, grinding teeth in extinct browsing horses and paleotheres, which both adapted to a diet of tough vegetation.
3. How is parallel evolution different from convergent evolution?
The primary difference lies in the ancestry of the species involved.
- In parallel evolution, two species with a relatively recent common ancestor evolve similar traits independently. They follow similar evolutionary paths because they share an underlying genetic potential.
- In convergent evolution, two species with a very distant or unrelated common ancestor evolve similar traits independently. For example, the wings of a bird and the wings of an insect are for flight, but their last common ancestor did not have wings.
4. What environmental conditions or drivers cause parallel evolution to occur?
Parallel evolution is primarily driven by similar selective pressures acting on species that share a common genetic background. Key drivers include:
- Similar Ecological Niches: When species occupy environments with comparable food sources, predators, and climate, they face the same challenges, promoting similar adaptations.
- Shared Developmental Pathways: Since the species share a common ancestor, their genetic toolkit for development is already similar. This makes it more likely for natural selection to favour mutations in the same genes, leading to parallel outcomes.
5. Why is studying parallel evolution important for understanding biology?
Studying parallel evolution is crucial because it provides strong evidence for the role of natural selection in shaping life. It demonstrates that evolution is not entirely random but can be predictable to some extent when environmental conditions are known. It shows that certain evolutionary pathways are more likely to occur than others, suggesting that the potential to develop complex traits can be inherent in a lineage's genetic makeup, waiting for the right environmental trigger.
6. How can parallel evolution create challenges in classifying organisms?
Parallel evolution can 'trick' biologists by making two distantly related species appear much more closely related than they are. Because they develop highly similar physical traits (phenotypes), early classification systems based solely on morphology might incorrectly group them together. To avoid this, modern biologists use molecular and genetic analysis (like DNA sequencing) to determine the true evolutionary relationships (phylogeny), which can reveal that the similarities are a product of parallel evolution, not a recent shared ancestry.
