Evolutionary radiation: Difference between revisions

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{{Distinguish|Adaptive radiation}}
An '''evolutionary radiation''' is an increase in [[Taxonomy (biology)|taxonomic]] diversity or [[morphology (biology)|morphological]] disparity, due to [[adaptation|adaptive]] change or the opening of [[ecospace]].<ref name=Wesley-Hunt2005>{{Cite journal| first1 = G. D. | title = The morphological diversification of carnivores in North America | url = | format = | journal = Paleobiology | volume = 31 | issue = | pages = 35–32 35–55| year = 2005| last1 = Wesley-Hunt | doi = 10.1666/0094-8373(2005)031<0035:TMDOCI>2.0.CO;2
}}</ref> 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 radiation]]s.<ref name=Schluter2000>{{cite book
| author = Schluter, D.
Perhaps the most familiar example of an evolutionary radiation is that of [[Eutheria|placental mammal]]s immediately after the [[extinction]] of the [[dinosaur]]s 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 [[shrew]]s. By the [[Eocene]] (58–37 million years ago), they had evolved into such diverse forms as [[bat]]s, [[whale]]s, and [[horse]]s.<ref>This topic is covered in a very accessible manner in Chapter 11 of [[Richard Fortey]]'s ''[[Life: An Unauthorised Biography]]'' (1997)</ref>
Other familiar radiations include the [[Cambrian explosion]], the [[Avalon explosion]], the [[Great Ordovician Biodiversification Event]], the [[Mesozoic–Cenozoic Radiation]], the radiation of land plants after their [[Evolutionary history of plants#land|colonisation of land]], the Cretaceous [[Evolutionary history of plants#Evolution_of_flowersEvolution of flowers|radiation of angiosperms]], and the diversification of insects, a radiation that has continued almost unabated since the [[Devonian]], {{Ma|400}}.<ref>The radiation only suffered one hiccup, when the [[Permo-Triassic extinction event]] wiped out many species.</ref>
==In the fossil record==
Much of the work carried out by [[palaeontology|palaeontologists]] studying evolutionary radiations has been using marine [[invertebrate]] [[fossil]]s simply because these tend to be much more numerous and easy to collect in quantity than large land [[vertebrate]]s such as [[mammal]]s or [[dinosaur]]s. [[Brachiopod]]s, for example, underwent major bursts of evolutionary radiation in the Early [[Cambrian]], Early [[Ordovician]], to a lesser degree throughout the [[Silurian]] and [[Devonian]], and then again during the [[Carboniferous]]. During these periods, different [[species]] of brachiopods independently assumed a similar morphology, and presumably mode of life, to species that had lived millions of years before. This phenomenon, known as [[homeomorphy]] is explained by [[convergent evolution]]: when subjected to similar selective pressures, organisms will often evolve similar adaptations.<ref>''Living and Fossil Brachiopods'' by M. J. S. Rudwick (1970)</ref> Further examples of rapid evolutionary radiation can be observed among [[ammonite]]s, which suffered a series of extinctions from which they repeatedly re-diversified; and [[trilobite]]s which, during the Cambrian, rapidly evolved into a variety of forms occupying many of the [[Ecological niche|niche]]s exploited by [[crustacean]]s today. <ref>''Aquagenesis, The Origins and Evolution of Life in the Sea'' by Richard Ellis (2001)</ref><ref>''Ammonites'' by Neale Monks & Philip Palmer (2002)</ref><ref>''Trilobite, Eyewitness to Evolution'' by Richard Fortey (2000)</ref>
==Recent examples==
A number of groups have undergone evolutionary radiation in relatively recent times. The [[cichlidae|cichlids]] in particular have been much studied by [[biology|biologists]]. In places such as [[Lake Malawi]] they have evolved into a very wide variety of forms, including species that are filter feeders, snail eaters, brood parasites, algal grazers, and fish-eaters.<ref>The Cichlid Fishes: Nature's Grand Experiment in Evolution by George Barlow (2002)</ref> [[Grass]]es have been another success, evolving in parallel with [[grazing]] [[herbivore]]s such as [[horse]]s and [[antelope]].<ref>[http://www.palaeos.com/Cenozoic/Cenozoic.htm Palaeos Cenozoic: The Cenozoic Era<!-- Bot generated title -->]</ref>
==See also==
* [[Evolutionary fauna]]