paximperium
Penultimate Amazing
- Joined
- May 30, 2008
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It's called Ring Speciation:There is a beautiful example given in Richard Dawkins' The Greatest Show On Earth of salamanders around a large lake somewhere in South America.
I can't remember the precise details, but as you make your way around the lake, you encounter salamanders that change in appearance quite drastically. The salamanders that are relatively close to each other as you go around the lake can interbreed, but are separated by distance, and therefore don't. If you put them in a cage together, however, they can.
But this is only the case with the salamanders that are relatively close to each other and, amazingly, only works clock-wise! If you take a salamander from the south-west and a salamander from the west, they can interbreed. Likewise, if you take a salamander from the east and a salamander from the south-east, they can interbreed. This works all the way around the lake. Side-by-side salamanders capable of breeding.
However, if you take a salamander from the south-west and try to breed it with a salamander from the south-east, it doesn't work! The micro-evolution happening gradually around the lake results in a different 'kind' of salamander, based on your definition of 'kind'. This is macro-evolution. The accumulation of micro-evolutionary changes over time.
Of course, you can now expand your definition of 'kind' accordingly.
Ring species show the process of speciation in action. In ring species, the species is distributed more or less in a line, such as around the base of a mountain range. Each population is able to breed with its neighboring population, but the populations at the two ends are not able to interbreed. (In a true ring species, those two end populations are adjacent to each other, completing the ring.) Examples of ring species are
- the salamander Ensatina, with seven different subspecies on the west coast of the United States. They form a ring around California's central valley. At the south end, adjacent subspecies klauberi and eschscholtzi do not interbreed (Brown n.d.; Wake 1997).
- greenish warblers (Phylloscopus trochiloides), around the Himalayas. Their behavioral and genetic characteristics change gradually, starting from central Siberia, extending around the Himalayas, and back again, so two forms of the songbird coexist but do not interbreed in that part of their range (Irwin et al. 2001; Whitehouse 2001; Irwin et al. 2005).
- the deer mouse (Peromyces maniculatus), with over fifty subspecies in North America.
- many species of birds, including Parus major and P. minor, Halcyon chloris, Zosterops, Lalage, Pernis, the Larus argentatus group, and Phylloscopus trochiloides (Mayr 1942, 182-183).
- the American bee Hoplitis (Alcidamea) producta (Mayr 1963, 510).
- the subterranean mole rat, Spalax ehrenbergi (Nevo 1999).
Watch the goalpost move.

