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Group Notes 24.3 - Fusion can be caused by environmental...

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Group Notes 24.3 Bryan Vowell Hybrid Zone: A region in which members of different species mate and produce offspring of mixed ancestry. Hybrids can exhibit either greater of less fitness with respect to the parent species. The hybrid zone (area of cross-breeding that separates two distinct species) often proves as a barrier restricting gene flow from one population to another. 3 possibilities for hybrid zones over time: 1. Reproductive barriers between species become strengthened over time resulting in decreasing production of hybrids. This case is referred to as Reinforcement (reinforcing the barrier) and is caused by natural selection’s effect on the mortality of a less fit hybrid group. 2. Reproductive barriers between species are weakened over time resulting in the fusion of two species into one.
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Unformatted text preview: Fusion can be caused by environmental effects on a species mating choice and over time cross breeding leads to a uniform gene pool (reverse of speciation) 3. Hybrids are continually produced creating a stable hybrid zone. This stability can be the result of a narrow gene barrier. Meaning that though a hybrid might be less fit than the either of the two species, hybrids continue to arise because the number of members of the two species mating amongst themselves accounts for the loss of hybrid offspring. Another case shows that hybrid stability could be the result of mating zone location. Though a hybrid might be more fit than the parent species fusion is prevented because the area in which the parent species would meet to mate is hostile to both species....
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