The evolution of California's wild radish has resulted in the extinction of its progenitors
The evolution of California's wild radish has resulted in the extinction of its progenitors
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DOI：
10.1111/j.0014-3820.2006.tb01197.x
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发表时间：
2006-06-01
期刊：
影响因子：
3.3
通讯作者：
Ellstrand, Norman C.
中科院分区：
文献类型：
--
作者：
Hegde, Subray G.;Nason, John D.;Ellstrand, Norman C.
如果两个先前分离的类群通过杂交和随后的双亲渗入相互同化，并且如果它们的渗入后代具有与亲本相同或更高的适应性，那么基因流应该通过杂种衍生物的替代而导致亲本类群的局部灭绝。这些戏剧性的事件可能会迅速发生，甚至在几代人的时间内发生。考虑到这种杂交灭绝可能发生的速度，可能很难确定该过程已经发生。因此，记录在案的因杂交而灭绝的例子很少见，尤其是在双亲都被杂交谱系取代的情况下。在这里，我们报告了加利福尼亚州两种 Raphanus 物种通过其杂交后代的替代而局部灭绝的形态学和等位酶证据。温室实验的结果表明，加州野生萝卜具有来自其祖先的特定性状组合，并且将我们的结果与早期报告的结果进行比较表明，纯亲本类型不再存在于野外。我们的结果还表明，与亲本相比，杂交衍生的谱系具有超出的果实重量。同种酶分析表明，加州野生萝卜源自推定亲本物种之间的杂交。然而，该分析还表明，加州野萝卜现在已成为与其父母分开的进化实体。我们认为，杂交后代谱系的侵略性殖民行为可能是由于亲本性状的新颖组合所致，而不是种群本身的遗传变异性。
If two previously isolated taxa mutually assimilate through hybridization and subsequent biparental introgression, and if their introgressed descendants have the same or higher fitness than their parents, then gene flow should result in the local extinction of parental taxa via replacement by hybrid derivatives. These dramatic events may occur rapidly, even in a few generations. Given the speed at which such extinction by hybridization may occur, it may be difficult to identify that the process has occurred. Thus, documented instances of extinction by hybridization are rare, and especially so for cases in which both parents are replaced by the hybrid lineage. Here we report morphological and allozyme evidence for the local extinction of two Raphanus species in California via replacement by their hybrid-derived descendants. The results from a greenhouse experiment demonstrate that California wild radishes have a specific combination of traits from their progenitors, and comparison of our results to that of an earlier report indicate that pure parental types are no longer present in the wild. Our results also show the hybrid-derived lineage has transgressive fruit weight compared to its parents. Allozyme analysis demonstrates that California wild radishes are derived from hybridization between the putative parental species. However, that analysis also demonstrates that California wild radish has now become an evolutionary entity separate from both of its parents. We suggest that the aggressive colonizing behavior of the hybrid-derived lineage probably results from a novel combination of parental traits, rather than genetic variability of the population per se.