Hybridization and Evolution in the Phlox pilosa Complex
Hybridization and Evolution in the Phlox pilosa Complex
复制标题
福禄考复合体的杂交和进化
DOI：
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发表时间：
1966
影响因子：
2.9
通讯作者：
Dale M. Smith
中科院分区：
文献类型：
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作者：
D. Levin;Dale M. Smith
福禄考类群的大量属性是中间或其他类群的组合，表明杂交可能在该属的进化中发挥了重要作用。在这方面特别感兴趣的是P. pilosa subsp，deamii和P. amoena subsp的起源。ligbtbipei是连接P.pilosa subsp. pilosa和P.amoena subsp，amoana.前一对以飞地的形式出现在它们的盟友的分布区域内，P. pilosa subsp，deamii分布在印第安纳州南部、肯塔基州西部和田纳西州西部，P. amoena subsp，ligbtbipei分布在格鲁吉亚的沿海平原。这些实体可以被解释为代表进化序列中的步骤，代表稳定的混合衍生物，或这些观点的组合。来自许多来源的证据强烈表明，P. pilosa subsp，deamii和P. amoena subsp，ligbtbipei是杂交的产物，然后快速固定某些重组类型。单从基因交换的角度来看，毛白杨和美丽白杨之间的基因交换障碍是中等的，而从基因交换的角度来看，两者之间的基因交换障碍是很强的。它们的花期在季节和持续时间上是相当的。它们同域分布于美国南部和东部的大片地区，但通常分布于不同的栖息地，P. pilosa subsp，pilosa是这一对中最中间的。然而，这些夹竹桃的生态可塑性是这样的，有时两者可能占据同一地点，从而提供了异花授粉的机会。穿越障碍是中等的，如果尝试几个穿越组合，可以突破。通过杂种的基因流动受到阻碍，这可以从它们的部分不育性得到证明，这具有基因和染色体的基础。已经发现了两个相当广泛的杂交实例。包括在自然桥，亚拉巴马，人口的杂交类型的阵列中的表型几乎相同的P. pilosa subsp，deamii和P. amoena subsp，lighthipei。后者的表型也出现在来自田纳西州帕森斯的第二个复合群体中的重组产物之一。这些地点都在这两个中间类群的范围之外。上述发现不仅证明了在自然种群中可以克服杂交的障碍，而且提供了确凿的证据，证明中间分类群的表型可以在P. pilosa subsp，pilosa和P. amoena subsp，amoena之间的杂交过程中合成，并且这些表型可以在中间生境中生存。我们认为，祖先P. araoena subsp，ligbtbipei和P. pilosa subsp，dearaii出现在类似于上述的群体中。这些植物可能已经成为建立在杂交种群附近，并产生了一系列高度可变的组合，这些组合在选择和遗传漂变的压力下进化成稳定的进化系。稳定只发生在沿沿着或附近的范围的周边P. amoena亚种，araoena。
The large number of Phlox taxa whose attributes are intermediate to or are a composite of those of other taxa suggests that hybridization may haveplayed a major role in the evolution of the genus. Of special interest in this regard are the origins of P. pilosa subsp, deamii and P. amoena subsp. ligbtbipei which bridge the morphological hiatis between P. pilosa subsp. pilosa and P. amoena subsp, amoana. The former pair occur as enclaves within the area of distribution of their allies, P. pilosa subsp, deamii in southern Indiana, western Kentucky, and western Tennessee and P. amoena subsp, ligbtbipei in the Coastal Plain of Georgia. These entities may be interpreted as representing steps in an evolutionary series, as representing stabilized hybrid derivatives, or a combination of these viewpoints. Evidence derived from a number of sources strongly suggests that P. pilosa subsp, deamii and P. amoena subsp, ligbtbipei are products of hybridization followed by the rapid fixation of certain recombinant types. The barriers to gene exchange between P. pilosa subsp, pilosa and P. amoena subsp, amoena are moderate when considered singly, strong when considered collectively. Their flowering periods are comparable in season and duration. They are sympatric throughout a large sector of the south, eastern United States, but typically occur in different habitats, P. pilosa subsp, pilosa being the most mesic of the pair. The ecological plasticity of these phloxes is such, however, that on occasion both may occupy the same site thus providing an opportunity for cross-pollination. The barriers to crossing are moderate and can be breached if several crossing combinations are attempted. Gene flow via the hybrids is hampered as evidenced by their partial sterility which has a genic and chromosomal basis. Two instances of rather extensive hybridization have been discovered. Included in the array of hybrid types in the Natural Bridge, Alabama, population were phenotypes virtually identical to P. pilosa subsp, deamii and also P. amoena subsp, lighthipei. The phenotype of the latter also appeared as one of the recombination products in the second composite population from Parsons, Tennessee. These localities are outside of the range of both intermediate taxa. Not only have the aforementioned discoveries demonstrated that the barriers to hybridization can be surmounted in natural populations, but they afford conclusive evidence that the phenotypes of the intermediate taxa can by synthesized during hybridization between P. pilosa subsp, pilosa and P. amoena subsp, amoena and that these phenotypes can survive in an intermediate habitat. We propose that the progenitors P. araoena subsp, ligbtbipei and P. pilosa subsp, dearaii arose in populations similar to those described above. These plants may have become established near the hybrid populations and have given rise to a series of highly variable assemblages which evolved into stable evolutionary lines under the pressures of selection and genetic drift. Stabilization has occurred only along or near the periphery of the range of P. amoena subsp, araoena.