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| | The Talk.Origins Archive Post of the Month: June 2006 (via CobWeb/3.1 planetlab2.cs.unc.edu) (Site not responding. Last check: 2007-10-06) |
 | | Although reproductive infertility or isolation is not something that selection "aims for", it is often a byproduct of changes made to the developmental cycle of the isolate population. |
 | | So, when the two get back in sympatry, they either can't interbreed (are isolated) or they can but the hybrids are not as fit as either of the parental variants (lowered hybrid fitness), and so they are then subjected to "reinforcing selection" to maintain isolation. |
 | | In this case a population of, say, flowering plants, is able to cross with some other species, but the progeny aren't thereby members of a new species, but backbreed into the population, changing its genetic constitution and adaptive niche so that when it is in sympatry with the original species, the population is now isolated. |
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