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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
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This occurs in cases where two subspecies are connected via one or more intermediate populations, each of which is in turn intermediate to its adjacent populations and exhibits more or less the same amount of
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are found that have the characteristics of both. There are two types of intergradation: primary and secondary intergradation.
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intergradation, and in these situations it is usually taken for granted that the clines are causally related (by
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difference that was achieved by the previously isolated
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88:will develop depending on the degree of
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59:as any other population within the
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38:is the way in which two distinct
133:Principles of Systematic Zoology
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42:are connected via areas where
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131:Mayr E, Ashlock PD (1991).
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79:Secondary intergradation
160:Hybridisation (biology)
73:environmental gradients
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170:Evolutionary biology
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110:Ring species
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57:variability
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154:Categories
116:References
98:subspecies
94:phenotypic
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18:Intergrade
104:See also
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