circular overlap

circular overlap

a naturally occurring arrangement of contiguous and intergrading populations which interbreed, curving round geographically until the beginning and end overlap and behave as good species. A species that behaves in this way is called a ring species. An example is the herring gull/black-backed gull species.
References in periodicals archive ?
A special case of geographic speciation is seen in ring species (polytypic species demonstrating circular overlap).
amplus may represent one divergent end of a ring species demonstrating circular overlap. According to this hypothesis, the relatively large P.
254-255) proposed that these two forms may be extremes of a single ring-species demonstrating circular overlap. Though he continues to regard these two mice as separate species in his taxonomy, his hypothesis, if verified, would necessitate the inclusion of the two forms within a single species.