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in biology, any gradual change in a particular characteristic of a population of organisms from one end of the geographical range of the population to the other. Gradients of characteristics usually accompany, and are responses to, environmental gradients; for example, a mountain range features gradients from top to bottom such as a temperature gradient (colder to warmer) and a humidity gradient (wetter to drier). They may also reflect patterns of individual migration or gene flow. In species of birds and mammals, there is usually a cline in body size, with smaller individuals in warm climates and larger individuals tending to be found in colder climates.



in biology, a gradual increase or decrease (quantitative gradient) of some character or property in populations in connection with marked change in physical geographic factors. A cline usually develops when a large area is more or less uniformly populated by a particular species and the populations and their groups are not separated by rigid isolating barriers. A cline provides an advantage in natural selection because it allows adjustment to any direction of change in the corresponding physical geographic factors.

A cline may also develop as a result of the rapid dispersal of a species.


Timofeev-Resovskii, N. V., N. N. Vorontsov, and A. V. Iablokov. Kratkii ocherk teorii evoliutsii. Moscow, 1969. Pages 163, 164, 171, 176.


A graded series of morphological or physiological characters exhibited by a natural group (as a species) of related organisms, generally along a line of environmental or geographic transition.


Patsy, original name Virginia Patterson Hensley. 1932--63, US country singer; her bestselling records include "Walking After Midnight", "I Fall to Pieces", and "Leavin' On Your Mind".
References in periodicals archive ?
When analyzed longitudinally, this character did not exhibit directional clinal variation, nor did adjacent samples differ.
Owen's (1963b) overall analysis of morphological variation in the Eastern Screech-Owl led him to reject the subspecies concept because of smooth clinal variation.
Beginning in central Maine (Bay 12), prevalence and infection intensity of prokaryotic inclusions showed a clinal trend with prevalence and infection intensity below the global median in the north and above the global median in Delaware Bay (Bay 36).
Age and growth of the bonnethead shark, Sphyrna tiburo, from northwest Florida, with comments on clinal variation.
Specifically, the particular distinctive clinal patterns of NR haplotypes over space mark trajectories of gene flow and, by inference, the origins and movement of populations (Underhill et al.
However, clinal variation is generally equal to or greater than the taxonomic variation.
One possibility is that the hawks in Quebec are larger than those in Ohio, a clinal difference that would agree with the classical Bergmann's rule (Bergmann 1847).
Most of the variation found was clinal between western and eastern populations, but comparisons between adjacent pairs of samples usually showed significant genetic differences.
This choice resulted from their decision to interpret the distribution of reptiles in Texas as essentially continuous and clinal.
However, one suboscine species, the Variable Antshrike (Thamnophilus caerulescens) exhibits clinal variation in a song characteristic that was concordant with variation in mitochondrial DNA among populations (Isler et al.
Allele 1 exhibited a clinal pattern, with highest frequencies in the northern sites.
These studies were conducted in different regions at separate times and may reflect clinal or temporal differences (or both) between Gulf of Mexico and northwestern Atlantic R.