|
|
|
|
Cline (population genetics)
|
| |
|
| |
In biology, a cline is a gradual change of phenotype (trait, character or feature) in a species over a geographical area, often as a result of environmental heterogeneity. This meaning of "cline" was introduced by Sir Julian Huxley.
Typically, a well-marked cline does not allow for a delineation of subspecies, as it is then impossible, by definition, to draw any further clear dividing lines between populations. In population genetics, a cline could include a spectrum of subspecies, as allele and haplotype frequencies tend to vary over a larger space; moreover, in evolution, genetic lineage sorting usually lags behind the establishment of locally-differentiated phenotypes.
Discussion
Ask a question about 'Cline (population genetics)' Start a new discussion about 'Cline (population genetics)' Answer questions from other users |
Encyclopedia
In biology, a cline is a gradual change of phenotype (trait, character or feature) in a species over a geographical area, often as a result of environmental heterogeneity. This meaning of "cline" was introduced by Sir Julian Huxley.
Typically, a well-marked cline does not allow for a delineation of subspecies, as it is then impossible, by definition, to draw any further clear dividing lines between populations. In population genetics, a cline could include a spectrum of subspecies, as allele and haplotype frequencies tend to vary over a larger space; moreover, in evolution, genetic lineage sorting usually lags behind the establishment of locally-differentiated phenotypes. Regardless, in neither case will such a variation yield different species, as long as the populations, though geographically spread, can interbreed one with another.
In the scientific study of human genetic variation, a gene cline can be rigorously defined, being readily submissible to straightforward, quantitative metrics; this has apparently not been so of the evidently more subjective concept of “race.”
Ring species
Ring species are a related concept, usually representing a wider linear range of genetic relationship than that typical of clines (within a single species). In ring species, however, the geographical distribution is circular (or “spiral”) in shape, so that the furthest ends of a cline overlap, one with another. But these two “end” populations rarely interbreed due to the cumulative effect of the many changes in phenotype along the cline. The populations elsewhere along the cline interbreed with their geographically adjacent populations as in a standard cline. Ring species present an interesting problem for those who seek to divide the living world into discrete species.
|
| |
|
|
