Joined: Sep. 2006
|Quote (jeannot @ April 11 2007,12:24)|
|Quote (Zachriel @ April 11 2007,12:02)|
|DaveScot † † |
|Dogs are possibly the most widely varying species on the planet while still remaining a single species. In 20,000 years of artificial selection and preservation of variants that never would have survived in the wild there hasnít been a single variant with an anatomical feature not characteristic of canines nor has a new species of dog emerged. |
It depends on you definition of "species". I'm sure some dog races are unable to reproduce with wolves.
Domestication has led to distinct specices. That's the case for a few crops, namely cultivated pea, broad bean, and even lentil (if I'm not mistaken), to name only legumes. They are never found in the wild. They have been completely differentiated from their wild ancestors, in just 10000 years of agriculture or less.
However, I don't know about polyploidy in those species.
Good point. That there may not be a distinct barrier between species is one area of evidence discussed by Darwin in Origin of Species. Lions can mate with Tigers and produce fertile offspring, but rarely do in the wild. Shipborne mice speciate rapidly into their new environments. Dogs rarely mate with wolves, but there may be some gene flow. Some dog breeds can't mate directly with certain other dog breeds, but there is substantial gene flow through intermediary breeds. Some plants can spontaneously speciate, and others just as quickly hybridize.