Intergradation
Encyclopedia
In zoology
, intergradation is the way in which two distinct subspecies
are connected via areas where populations are found that have the characteristics of both. There are two types of intergradation:
Primary intergradation:
Occurs in cases were two subspecies are connected via one or more intermediate populations, each of which are in turn intermediate to their adjacent populations and exhibit more or less the same amount of variability as any other population within the species
. Adjacent populations and subspecies are subject to cline
intergradation, and in these situations it is usually taken for granted that the clines are causally related (by selection) to environmental gradient
s.
Secondary intergradation:
When contact between a geographically isolated subspecies is reestablished with the main body of the species or with another isolate subspecies, interbreeding takes place as long as the isolate has not yet evolved an effective set of isolating mechanisms. Consequently, a relatively distinct zone or belt of hybridization will develop depending on the degree of genetic and phenotypic difference that was achieved by the previously isolated subspecies
.
Zoology
Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...
, intergradation is the way in which two distinct subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
are connected via areas where populations are found that have the characteristics of both. There are two types of intergradation:
Primary intergradation:
Occurs in cases were two subspecies are connected via one or more intermediate populations, each of which are in turn intermediate to their adjacent populations and exhibit more or less the same amount of variability as any other population within the species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
. Adjacent populations and subspecies are subject to cline
Cline (population genetics)
In biology, an ecocline or simply cline describes an ecotone in which a series of biocommunities display continuous gradient...
intergradation, and in these situations it is usually taken for granted that the clines are causally related (by selection) to environmental gradient
Environmental gradient
An environmental gradient is a gradual change in abiotic factors through space . Environmental gradients can be related to factors such as altitude, temperature, depth, ocean proximity and soil humidity....
s.
Secondary intergradation:
When contact between a geographically isolated subspecies is reestablished with the main body of the species or with another isolate subspecies, interbreeding takes place as long as the isolate has not yet evolved an effective set of isolating mechanisms. Consequently, a relatively distinct zone or belt of hybridization will develop depending on the degree of genetic and phenotypic difference that was achieved by the previously isolated subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
.