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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 ?
The resulting cline in allele frequencies is given by the equilibrium solution of (2)
0] is the (arbitrary) center of the cline at which p = (Bazykin 1969).
In this model, the difference in mean fitness between populations at the center and the edge of the cline is [s.
Besides cline width, cline shape can also be used in analyzing hybrid zone.
In describing the cline shape, I will use an independent variable x', the deviation from the center of the cline normalized to the half of the width of the hybrid zone, x[prime] = (x - [x.
If A [greater than] 0 and B [not equal to] 0, the cline p = p (x) is implicitly defined by
In the case of both fertility and viability selection, the difference in mean fitness between populations at the center of the cline and the edge is
B] the cline width produced by viability selection only with s = [Delta], where [Delta] is the heterozygote's reduction in fitness.
Figure 1 compares the cline shape in several models using a logit scale (i.
The cline is wider by a factor [square root or 2] than Bazykin's cline and the cline shape described by (14b) deviates from that of Bazykin's cline significantly.