primary intergradation

primary intergradation

a region of intermediate characteristics between two distinct phenotypic populations that has arisen through SELECTION.
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Mayr defined primary intergradation as clinal variation that develops within a continuous series of populations and secondary intergradation as the consequence of junction between populations that have become differentiated in allopatry.
1978) as the indication that the Iberian Peninsula was a large area of primary intergradation between A.
If the hypothesis of primary intergradation is correct, we expect the genetic variability of populations to show gradual modifications at microsatellite loci along the transect, with a possible reduction northward due to colonization effects dependent on age.
Second, hybrid zones could arise from primary intergradation due to differential selection along an environmental gradient (Endler 1977).
Stebbins' concept of a polytypic ring species was based on perceived primary intergradation between the sub-species where they met, with the exception of two instances of postulated secondary contact.
Central to the concept of Ensatina as a ring species is the primary intergradation of the unblotched oregonensis populations at the head of the Sacramento Valley with the blotched platensis populations of the northern Sierra Nevada, the southern Cascades, and intervening mountains.
A more gradual cline would suggest primary intergradation and lack of genetic isolation between distinct northern and southern types.
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