箭根薯（薯蓣科）的遗传多样性与地理分化：一种具有艳丽花朵展示的自主自花授粉植物。
Genetic diversity and geographic differentiation in Tacca chantrieri (Taccaceae): an autonomous selfing plant with showy floral display.
作者信息
Zhang Ling, Li Qing-Jun, Li Hong-Tao, Chen Jin, Li De-Zhu
机构信息
Laboratory for Plant Biodiversity and Biogeography, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650204, China.
出版信息
Ann Bot. 2006 Aug;98(2):449-57. doi: 10.1093/aob/mcl123. Epub 2006 Jun 21.
BACKGROUND AND AIMS
Despite considerable investment in elaborate floral displays, Tacca chantrieri populations are predominantly selfing. It is hypothesized that this species might possess considerable spatial or temporal variation in outcrossing rates among populations. To test this hypothesis, genetic variability and genetic differentiation within and among T. chantrieri populations were investigated to find out if they are in agreement with expectations based on a predominantly inbred mating system.
METHODS
Genetic diversity was quantified using inter-simple sequence repeats (ISSR) in 303 individuals from 13 populations taken from known locations of T. chantrieri in China, and from one population in Thailand.
KEY RESULTS
Of the 113 primers screened, 24 produced highly reproducible ISSR bands. Using these primers, 160 discernible DNA fragments were generated, of which 145 (90.62 %) were polymorphic. This indicated considerable genetic variation at the species level. However, there were relatively low levels of polymorphism at population levels, with percentages of polymorphic bands (PPB) ranging from 8.75 % to 55 %. A high level of genetic differentiation among populations was detected based on different measures (Nei's genetic diversity analysis: G(ST) = 0.5835; AMOVA analysis: F(ST) = 0.6989). Furthermore, based on levels of genetic differentiation, the 14 populations clustered into two distinct groups separated by the Tanaka Line.
CONCLUSIONS
High levels of differentiation among populations and low levels of diversity within populations at large spatial scales are consistent with earlier small-scale studies of mating patterns detected by allozymes which showed that T. chantrieri populations are predominantly selfing. However, it appears that T. chantrieri has a mixed-mating system in which self-fertilization predominates, but there is occasional outcrossing. Significant genetic differences between the two distinct regions might be attributed to vicariance along the Tanaka Line. Finally, possible mechanisms of geographic patterns based on genetic differentiation of T. chantrieri are discussed.
背景与目的
尽管在精心设计的花卉展示上投入了大量资金，但箭根薯种群主要进行自花授粉。据推测，该物种在种群间的异交率可能存在相当大的空间或时间变异。为了验证这一假设，对箭根薯种群内部和种群之间的遗传变异性和遗传分化进行了研究，以确定它们是否符合基于主要自交交配系统的预期。
方法
利用简单序列重复区间（ISSR）对来自中国箭根薯已知分布地点的13个种群以及泰国的1个种群的303个个体进行遗传多样性定量分析。
主要结果
在筛选的113个引物中，24个产生了高度可重复的ISSR条带。使用这些引物，共产生了160个可分辨的DNA片段，其中145个（90.62%）具有多态性。这表明该物种在物种水平上存在相当大的遗传变异。然而，在种群水平上多态性水平相对较低，多态性条带百分比（PPB）在8.75%至55%之间。基于不同的测量方法（Nei遗传多样性分析：G(ST)=0.5835；AMOVA分析：F(ST)=0.6989）检测到种群间存在高水平的遗传分化。此外，基于遗传分化水平，14个种群聚为两个不同的组，由田中线分隔。
结论
在大空间尺度上，种群间的高分化水平和种群内的低多样性水平与早期通过等位酶检测到的交配模式的小规模研究结果一致，该研究表明箭根薯种群主要进行自花授粉。然而，箭根薯似乎具有一种混合交配系统，其中自花受精占主导，但偶尔也会发生异交。两个不同区域之间的显著遗传差异可能归因于沿田中线的地理隔离。最后，讨论了基于箭根薯遗传分化的地理格局的可能机制。
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