Evolutionary radiation

Source: Wikipedia, the free encyclopedia.
Not to be confused with Adaptive radiation.
Evolutionary radiations during the Phanerozoic.

An evolutionary radiation is an increase in

epoch) is often referred to as an explosion. Radiations may affect one clade or many, and be rapid or gradual; where they are rapid, and driven by a single lineage's adaptation to their environment, they are termed adaptive radiations.[3]

Examples

Perhaps the most familiar example of an evolutionary radiation is that of placental mammals immediately after the extinction of the non-avian dinosaurs at the end of the Cretaceous, about 66 million years ago. At that time, the placental mammals were mostly small, insect-eating animals similar in size and shape to modern shrews. By the Eocene (58–37 million years ago), they had evolved into such diverse forms as bats, whales, and horses.[4]

Other familiar radiations include the

Mesozoic–Cenozoic Radiation, the radiation of land plants after their colonisation of land, the Cretaceous radiation of angiosperms, and the diversification of insects, a radiation that has continued almost unabated since the Devonian, 400 million years ago.[5]

Types

Adaptive radiations involve an increase in a clade's speciation rate coupled with divergence of morphological features that are directly related to ecological habits; these radiations involve speciation not driven by geographic factors and occurring in sympatry; they also may be associated with the acquisition of a key trait.[6] Nonadaptive radiations arguably encompass every type of evolutionary radiation that is not an adaptive radiation,[7][8] although when a more precise mechanism is known to drive diversity, it can be useful to refer to the pattern as, e.g., a geographic radiation.[1] Geographic radiations involve an increase in speciation caused by increasing opportunities for geographic isolation.[1] Radiations may be discordant, with either diversity or disparity increasing almost independently of the other, or concordant, where both increase at a similar rate.[2] Where the mechanism of diversification is ambiguous and the species seem to be closely related, sometimes the terms "species radiation," "species flock" or "species complex" are used.[9]

In the fossil record

Much of the work carried out by

ammonites, which suffered a series of extinctions from which they repeatedly re-diversified; and trilobites which, during the Cambrian, rapidly evolved into a variety of forms occupying many of the niches exploited by crustaceans today.[11][12][13]

Recent examples

A number of groups have undergone evolutionary radiation in relatively recent times. The

Grasses have been a success, evolving in parallel with grazing herbivores such as horses and antelope.[16]

See also

References

  1. ^
    PMID 26632984
    .
  2. ^
    S2CID 10989917
    .
  3. ^ Schluter, D. (2000). The Ecology of Adaptive Radiation. Oxford University Press.
  4. Life: An Unauthorised Biography
    (1997)
  5. Permo-Triassic extinction event
    wiped out many species.
  6. S2CID 4004118
    .
  7. S2CID 73494468
    .
  8. PMID 19409647
    .
  9. PMID 31943081
    .
  10. ISBN 9780091030810
    .
  11. ^ Aquagenesis, The Origins and Evolution of Life in the Sea by Richard Ellis (2001)
  12. ISBN 978-1588340474
    .
  13. ISBN 9780002570121
    .
  14. ^ The Cichlid Fishes: Nature's Grand Experiment in Evolution by George Barlow (2002)
  15. ^ Parallel Adaptive Radiations - Caribbean Anoline Lizards. Todd Jackman. Villanova University. Retrieved 10 September 2013.
  16. ^ Palaeos Cenozoic: The Cenozoic Era Archived 2008-11-06 at the Wayback Machine
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