adaptive radiation


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adaptive radiation,

in biology, the evolution of an ancestral species, which was adapted to a particular way of life, into many diverse species, each adapted to a different habitat. Adaptive radiation has occurred in the evolution of many groups of organisms, and is clearly illustrated by Hawaiian honey-creepers. Another example is shown in Darwin's finchesDarwin's finches
or Galapagos finches
, species of small perching birds, constituting the subfamily Geospizinae of the tanager family. Not related to the true finches, this group of at least fifteen species is confined to the Galápagos Islands, except for a
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, at least 15 species of small land birds of the Galápagos Islands and Cocos Island. All of Darwin's finches derive from a single species of ground-dwelling, seed-eating finch that probably emigrated from the South American mainland. Because the environmental niches, or habitats, were unoccupied on the isolated islands, the ancestral stock was able to differentiate into diverse species; several species are ground-dwelling seedeaters, others live on cactus plants or trees and are seedeaters or insecteaters. See also competitioncompetition,
in biology, relationship between members of the same or different species in which individuals are adversely affected by those having the same living requirements, such as food or space. Intraspecific competition, i.e.
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.

Adaptive Radiation

 

the formation of diverse organismic forms within the limits of a species or a group of related species. The term was proposed by the American scientist H. Osborn in 1915, although the idea had already been advanced by C. Darwin, who employed the term “divergence.” Adaptive radiation is fundamental to all forms of adaptogenesis and is the result of the acquisition by organisms of special accommodations—adaptations and penetrations into new adaptive zones. The main origin of adaptive radiation is found in intraspecies processes such as genetic diversity of species populations, differentiation of the species into geographical and ecological races as a result of enlargement of the territory under favorable conditions, and intraspecies contradictions.

The scale of adaptive radiation may differ from one case to another. Large-scale adaptive radiation is found in the evolution of amphibians, some aquatic forms of which have tails (Urodela), while strictly amphibious forms preserve the tail only in the larval stage (Anura), and a third group, the dry-land forms, have lost their legs and assumed a serpentine character (Apoda). Examples of small-scale adaptive radiation associated with the formation of geographical races are found in the cases of the Kamchatka great spotted woodpecker (Dendrocopus major Kamtschaticus ) and the Talysh lesser spotted woodpecker (Dendrocopus minor quadrifasciatus ) or in races of the ordinary spruce—Norway (Picea excelsa), Siberian (Picea obovata), and Finnish (Picea fennica).

A. V. IABLOKOV

adaptive radiation

[ə′dap·tiv ‚rād·ē′ā·shən]
(evolution)
Diversification of a dominant evolutionary group into a large number of subsidiary types adapted to more restrictive modes of life (different adaptive zones) within the range of the larger group.
References in periodicals archive ?
However, the geographic context of speciation in situations of adaptive radiation, where multiple close relatives occur in sympatry, is still the subject of considerable debate (Glor et al.
A premier example of adaptive radiation in plants is the Hawaiian silversword alliance, an endemic lineage in the sunflower family (Asteraceae).
With a new analysis of two such adaptive radiations in the fossil record, researchers discovered that these diversifications proceeded head-first.
Overall, the project will integrate information on the distribution of genes controlling ecological, behavioural and genetic differences between species with patterns of recombination, in order to understand the process of genome divergence and adaptive radiation.
These lizards have been compared to Darwin's finches and in many respects they are similar," said Jonathan Losos, an author of the paper, professor at Harvard University, and author of the book 'Lizards in an Evolutionary Tree: Ecology and Adaptive Radiation of Anoles'.
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