Kline (biology)

As Kline (also Klin or Ökokline , English: cline or ecocline ; from Greek .: κλίνω: lean, prone), the continuous change of a biological feature, in parallel with a Ökogradienten (also see gradient ), respectively. It is a directed variation of the characteristic expression and the underlying genetic range of variation of a species .

causes

The triggering factor does not have to be known in detail because several factors often change in parallel in a way that is difficult to resolve, for example along the geographical latitude or the mountain height. The change in characteristics can be a pure environmental modification, but often also has a genetic basis. To distinguish these cases, breeding is usually carried out under controlled environmental conditions (in the laboratory or in the greenhouse). If the difference persists even under these conditions, it must be genetic. This gradual change in frequency of the trait-determining alleles is also referred to as a kline .

The explanation of genetic clinics is a problem in evolutionary biology because the genetic exchange or gene flow between individuals and subpopulations should actually homogenize such differences. A kline can persist if either the gene flow is lower than expected or the selection is strong enough to maintain the difference despite the homogenizing effect of the gene flow. The formation of a genetic cline can be an extremely rapid process. In the case of fruit flies of the species Drosophila subobscura introduced to America , 20 years was enough to generate a hereditary size gradient in wing length between northern and southern populations.

Klinen are often named after the factor with which the observed population or species variation is correlated. So z. For example, a “thermocline” is a change in characteristics (or an allele gradient) along a temperature gradient. A change in characteristics along an ecological environmental factor, or several changes that change in parallel, is generally referred to as an "ecocline". However, some scientists also call the causative factor gradient itself (or the corresponding sequence of habitats or locations) that. In this sense, the term can then also be applied to entire communities. Most scientists prefer the term “ ecotone ” in this case .

Examples

• In many mammals and birds , the body size increases with increasing latitude ( Bergmann's rule )
• The color of the wings of the rapeseed white varies from light to dark. The further north you go in Scandinavia, the darker the wings are.

See also

• Polymorphism
• Ecotype
• Ring species

Individual evidence

1. ↑ Ulrich Kull: Evolution. Metzler, Stuttgart 1977/78, p. 139.
2. ↑ Andrew Cockburn: Evolutionary Ecology. G. Fischer, Stuttgart 1995, ISBN 978-3-437-30775-1 , p. 253.
3. ^ Heinrich Walter, Siegmar-W. Breckle (ed.): Ecology of the earth. Volume 1: Ecological basics from a global perspective. Schweizerbart, 1991, p. 190 ff.
4. ^ Gemoll: Greek-German school and hand dictionary. 1908.
5. ^ Douglas J. Futuyma: Evolutionary Biology. Birkhäuser, Basel 1990, ISBN 978-3-7643-2200-7 , pp. 119ff.
6. ^ Paul R. Ehrlich, Peter H. Raven: Differentiation of Populations. In: Science. 165: 1228-1232 (1969).
7. ↑ JBS Haldane: The theory of a cline. In: Journal of Genetics. 48 (3) 1948, pp. 277-284.
8. ↑ Raymond B. Huey, George W. Gilchrist, Margen L. Carlson, David Berrigan, Luis Serra: Rapid Evolution of a Geographic Cline in Size in an Introduced Fly. In: Science. 287 (2000), pp. 308-309.
9. ↑ Eddy van der Maarel: Ecotones and Ecoclines are different. In: Journal of Vegetation Science. 1 (1990), pp. 95-98.
10. ^ Ulrich Kull: Evolution , Metzler, Stuttgart 1977/78, p. 139