Ring species is a term introduced by Arthur Cain when elaborating on speciation [Error: Wrong macro arguments: "2851" for macro 'ref' (maybe wrong macro tag syntax?)]
. Ring species consist of overlapping populations with only subtle differences. The traits change continuously, so that the more geographically distant the more pronounced the differences. Only on both sides of a geographical barrier there are sharp differences between the populations' traits.
A ring species is illustrated by the picture below.
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The mountain ridge symbolizes a geographical barrier. But a geographical barrier can be any geographical obstacle to a species dissemination depending on a species capabilities to move, a river or a highway for instance.
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