Convergent evolution of SARS-CoV-2: Will it reduce the pandemic on its own?
Convergent vs. Divergent evolution:
Convergent evolution is when two species develop similar characteristics even though they lack a recent common ancestor.
Convergent evolution, seen in all biological kingdoms, results from natural selection. By sharing a common or similar ecological niche, two independent and unrelated species benefit from developing the same functional features. They undergo independent evolution but develop similar body forms or functional characteristics.
The best example would be — fish and dolphins. Both are vastly different animals. Their underlying DNA sequences and nervous systems are different. However, they have developed similar structures (fins) because they inhabit identical environmental conditions. Their fins might have evolved differently, but they serve a common purpose. Dolphins, being placental animals, have their fins closely related to the human hand. But fish fins come from a different genetic source.
Divergent evolution is the opposite of convergent evolution, where though two species share a common ancestor, they evolve to become increasingly different over time. They will end up becoming separate species.
The best example would be — bats and mice. Though both share a recent common ancestor, divergent evolution has transformed them into two entirely different species. Bat wings are equivalent to mice’s front paws. But they have spread apart, forming a fleshy webbing. Both are homologous structures with a common origin, but they serve a different purpose.
Evolution of SARS-CoV-2 in the pandemic
Each time the virus infects people, it makes copies of itself — an error-prone process. Many of these errors are insignificant, but those that give it a survival advantage tend to persist.
A few experiments exposed the virus to antibodies and demonstrated how the virus develops mutations, including the E484K mutation.
SARS-CoV-2 has generated several variants that differ from their ancestral strain.
The newer variants — UK, South African, and Brazilian — have been impacting the pandemic with higher transmissibility, reduced protection from vaccines, and evasion of natural immunity developed from previous SARS-CoV-2 infection/ COVID-19 episode.
Convergent evolution with SARS-CoV-2:
Recent mutations seen in different parts of the world might have developed independently but are similar to each other — a phenomenon that describes “convergent evolution.” While it may continue to mutate, scientists feel that very few significant mutations might be left in its arsenal.
A recent study published in Feb 2021 demonstrated simultaneous convergent evolution.
SARS-CoV-2 may have a limited number of mutations that it can sustain before compromising its fitness — or changing so much that it no longer remains the same virus.
“It is plausible that this virus has a relatively limited number of antibody escape mutations it can make before it has played all of its cards” — Shane Crotty (virologist, La Jolla Institute for Immunology, San Diego).
Predicting the evolution of the virus and how it will mutate is challenging. However, if the fixed number of moves and convergent evolution is true, it would simplify things for vaccine developers.
References:
- Convergent Evolution Explained With Examples https://www.masterclass.com/articles/convergent-evolution-explained.
- Emergence in late 2020 of multiple lineages of SARS-CoV-2 Spike protein variants affecting amino acid position 677. MedRxiv, 14 Feb 2021. Link: https://www.medrxiv.org/content/10.1101/2021.02.12.21251658v1
- Analysis-in mutant variants, has the coronavirus shown its best tricks? https://www.mdlinx.com/news/analysis-in-mutant-variants-has-the-coronavirus-shown-its-best-tricks/73kYeSvqCA9JUw2k7eQQRk
