Low levels of intraspecific genetic variation at a rapidly evolving chloroplast DNA locus in North American duckweeds (Lemnaceae)
Low levels of intraspecific genetic variation at a rapidly evolving chloroplast DNA locus in North American duckweeds (Lemnaceae)
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DOI：
10.2307/2446212
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发表时间：
1996-04-01
影响因子：
3
通讯作者：
Neigel, JE
中科院分区：
文献类型：
--
作者：
Jordan, WC;Courtney, MW;Neigel, JE
尽管以往大多数关于植物叶绿体（cp）DNA变异的研究都集中在物种水平以上的系统学和进化方面，但叶绿体DNA的种内变异是常见的，并且为种群水平的进化过程提供了有用的见解。我们使用聚合酶链反应方法检测了来自美国南部和东部的浮萍属（紫萍和浮萍）种群内部及种群之间叶绿体rpL16基因的限制性位点和序列变异。据我们所知，rpL16区域此前尚未被用于研究自然界中的叶绿体DNA变异。虽然在物种之间检测到了相当多的限制性位点和序列变异，但在选择进行序列分析的两个物种（紫萍和浮萍）的种群内部均未发现变异，并且紫萍没有种群间变异。在浮萍中鉴定出两种叶绿体DNA单倍型，其中一种单倍型仅限于路易斯安那州的三个地点，另一种在所有其他采样种群中都有发现。这种变异的缺乏不能简单地解释为低突变率的结果。一般来说，第二组内含子似乎受到很少的功能限制，特别是在叶绿体rpL16内含子中，物种之间已经发现了广泛的序列差异。然而，诸如历史分布范围的扩张和收缩、奠基者效应、当地种群规模的波动以及自然选择等因素可能在降低这些物种的叶绿体DNA序列变异性方面起到了作用。
Although most previous studies on chloroplast (cp) DNA variation in plants have concentrated on systematics and evolution above the species level, intraspecific variation in cpDNA is common and has provided useful insights into population-level evolutionary processes. Polymerase chain reaction methods were used to examine restriction site and sequence variation in the chloroplast rpL16 gene within and among populations of duckweed species (Spirodela and Lemna) from the southern and eastern United States. To our knowledge, the rpL16 region has not previously been used to investigate cpDNA variation in nature. While considerable restriction site and sequence variation were detected among species, no variation was found within populations of either of the two species (S. punctata and L. minor) selected for sequence analysis, and S. punctata showed no interpopulational variation. Two cpDNA haplotypes were identified in L.,ninor, with one haplotype restricted to three sites in Louisiana and the other found in all other populations sampled. This paucity of variation cannot be readily explained as the result of a low mutation rate. In general, group II introns appear to be subject to very little functional constraint, and extensive sequence differences have been found between species in the chloroplast rpL16 intron in particular. However, factors such as historical range expansions and contractions, founding effects, fluctuations in local population size. and natural selection may play a role in reducing cpDNA sequence variability in these species.