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Adaptive Radiation Definition
In the Galapagos Islands, Charles Darwin noticed a variety of finches. These finches vary in their beak shape and overall size. This is adaptive radiation and natural selection at work.
Adaptive Radiation and Darwin’s Finches
Darwin’s finches are used to illustrate adaptive radiation. Adaptive radiation is the process where all the species derived from a common ancestor adapted to their environment over time. This adaptation occurs via natural selection. The finches are previously found in the South American mainland, but over time they occupy the Galapagos Islands, which is 600 miles away from the mainland.
The ecological niche has little competition that is occupied by the finches. Due to little competition and favorable conditions, the population began to flourish and intraspecific competition starts between the population. After some time, the resources in the island start squeezing that do not allow the finches to sustain for long.
The conditions such as the mechanism of natural selection, and changes in the gene pool allow the finches to adapt to the environment. As the competition increases, the finches start to find new ecological niches to sustain in less competition for a long period. The finches adapted to their environment and start using various food sources available on the island.
Over time, the diversifying finches get a better chance of survival due to adaptation and natural selection whereas the original finches might have disappeared. Adaptation to their environment allows the finches to survive in harsh environmental conditions for a longer-term. The process of adaptation occurs via natural selection.
Adaptive Radiation Examples
The Marsupials
The Marsupial mammals are native to Australia. These mammals bear their young inside a pouch, therefore, differ from other mammals. Long ago, there is only one single continent present the landmass of earth, which is named Pangaea. All the land animals exist on this continent.
Later, fragmentation in this continent made a geographical barrier that restricted the mammals of this time to reproduce with one another. The barrier enables the group of animals to increase their gene pool differently as they could not reproduce with one another. Thus the marsupial family of mammals occurs in Australia.
Therefore all the members of the marsupial family would have been evolved from a common ancestor. However, over time all the marsupial members adapted to their environment via natural selection and occupy their ecological niche.
For example, kangaroo and koalas are evolved from the same common ancestors but have different characteristics, kangaroos have long powerful legs that allow them to cover long distances whereas koalas consist of smaller structures and a centralized center of gravity that allows them to climb in trees to obtain food.
Humans
The most evolved species on earth are humans. Humans over time undergone various adaptations and changes from their ancestors. The examples include:
• They can walk on two of their limbs and adapted to use their other two limbs (hands or arms) for various tasks such as typing, tying, and various other common tasks.
• Our skin also adapts according to our environment and represents different amounts of melanin that results in dark-skinned people and light-skinned people.
• The body structure also changes with the temperature in our climate. For example, humans living in the cold environment produce broader and smaller offspring whereas, in hotter environments, they produce thinner and taller humans.
It is quite possible that different species could spawn from their own if two groups of humans were isolated over time. It happens because two groups will adapt to their environment. This means that when two groups could not reproduce with another and produce fertile offspring, the gene pool in each group changes over time. At this condition, a species has begun from any species.
Adaptive Radiation Citations
- Molecular evolution, adaptive radiation, and geographic diversification in the amphiatlantic family Rapateaceae: evidence from ndhF sequences and morphology. Evolution . 2000 Dec;54(6):1915-37.
- Evolution of Lower Brachyceran Flies (Diptera) and Their Adaptive Radiation with Angiosperms. Front Plant Sci . 2017 Apr 24;8:631.
- Adaptive radiation versus ‘radiation’ and ‘explosive diversification’: why conceptual distinctions are fundamental to understanding evolution. New Phytol . 2015 Jul;207(2):297-303.
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