Ring species

The coloured bars show a number of natural populations, each population represented by a different colour, varying along a cline (a gradual change in conditions which gives rise to slightly different characteristics predominating in the organisms that live along it). Such variation may occur in a straight line (for example, up a mountain slope) as is shown in A, or may bend right around (for example, around the shores of an ocean), as is shown in B.

In the case where the cline bends around, populations next to each other on the cline can interbreed, but at the point that the beginning meets the end again, as is shown in C, the differences that have accumulated along the cline are great enough to prevent interbreeding (represented by the gap between pink and green on the diagram). The interbreeding populations in this circular breeding group are then collectively referred to as a ring species.

The Larus gulls interbreed in a ring around the arctic. 1: L. fuscus, 2: Siberian population of Larus fuscus, 3: L. heuglini, 4: L. vegae birulai, 5: L. vegae, 6: L. smithsonianus, 7: L. argentatus.

Herring gull (Larus argentatus) (front) and a lesser black-backed gull (Larus fuscus) (behind) in Norway: two phenotypes with clear differences

Speculated evolution and spread of the greenish warbler.
  P. t. trochiloides
  P. t. obscuratus
  P. t. plumbeitarsus
  P. t.

In biology, a ring species is a connected series of neighbouring populations, each of which can interbreed with closely sited related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed, though there is a potential gene flow between each "linked" population. Such non-breeding, though genetically connected, "end" populations may co-exist in the same region thus closing a "ring". The German term Rassenkreis, meaning a ring of populations, is also used.

单词	Rassenkreis
释义	Rassenkreis 英语百科 Ring species In biology, a ring species is a connected series of neighbouring populations, each of which can interbreed with closely sited related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed, though there is a potential gene flow between each "linked" population. Such non-breeding, though genetically connected, "end" populations may co-exist in the same region thus closing a "ring". The German term Rassenkreis, meaning a ring of populations, is also used.
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