Multiple independent formations of Tragopogon tetraploids (Asteraceae): evidence from RAPD markers
Multiple independent formations of Tragopogon tetraploids (Asteraceae): evidence from RAPD markers
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DOI：
10.1046/j.1365-294x.1998.00453.x
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发表时间：
1998-10-01
影响因子：
4.9
通讯作者：
Soltis, DE
中科院分区：
文献类型：
--
作者：
Cook, LM;Soltis, PS;Soltis, DE
多倍体被广泛认为是导致植物新物种形成的重要力量。据估计，被子植物中多倍体起源的物种数量高达约50%;然而，尽管如此，多倍体进化的许多方面仍然知之甚少。最近的研究表明，多倍体物种的循环起源是规则而不是例外。本研究是为数不多的旨在量化多倍体物种独立起源数量的研究之一。本文报道了两个四倍体物种Tragopogon mints和T.在过去的50年里，在华盛顿东部的帕卢塞地区和邻近的北方爱达荷州出现了miscellus（菊科）。以前的工作利用形态学，cpDNA和rDNA限制性位点分析，等位酶，细胞学，和黄酮类化合物化学确定T。mirus至少出现过5次，T.在帕卢塞上至少吃了两次。为了更严格地评估这些物种的多个起源的频率，七个种群的T。mirus和三个群体的T. miscellus是无法区分的基础上以前的标记进行了调查，使用随机扩增多态性DNA（RAPD）标记，从同一网站的二倍体祖先物种的人口也进行了分析。每个四倍体种群都有一个独特的RAPD标记谱，这表明每个调查的种群起源独立于该地区的其他种群。只有两个四倍体的人口相结合的RAPD标记发生在同一地点的二倍体祖先的配置文件。这两个多倍体物种，其范围和数量大大增加，因为他们在20世纪早期形成，已形成反复在当地的地理规模和在很短的时间内。此外，每个四倍体物种的传播主要不是通过传播来自单一种群的繁殖体，而是通过重复的、独立的多倍体化事件来重建多倍体分类群。
Polyploidy is widely recognized as a significant force leading to the formation of new plant species. Estimates of the number of angiosperm species with polyploid origins are as high as approximate to 50%; however, in spite of this prevalence, many aspects of polyploid evolution remain poorly understood. Recent studies have suggested that recurrent origins of polyploid species are the rule rather than the exception. The present study is one of only a few designed to quantify the number of independent origins of a polyploid species. The two tetraploid species Tragopogon mints and T. miscellus (Asteraceae) arose within the past 50 years in the Palouse region of eastern Washington and adjacent northern Idaho. Previous work using morphology, cpDNA and rDNA restriction site analyses, allozymes, cytology, and flavonoid chemistry established that T. mirus had arisen at least five times, and T. miscellus at least twice, on the Palouse. To assess the frequency of multiple origins of these species more rigorously, seven populations of T. mirus and three populations of T. miscellus that were indistinguishable based on previous markers were surveyed using random amplified polymorphic DNA (RAPD) markers; populations of the diploid progenitor species from the same sites were also analysed. Each tetraploid population had a unique RAPD marker profile, suggesting that each population surveyed originated independently of the other populations in the region. Only two of the tetraploid populations combined the RAPD marker profiles of the diploid progenitors occurring at the same site. Both polyploid species, whose ranges and numbers have greatly increased since their formation in the early part of the twentieth century, have formed repeatedly on a local geographical scale and during a short time frame. Furthermore, each tetraploid species is spreading not primarily by dispersal of propagules from a single population of origin, but through repeated, independent polyploidization events that recreate the polyploid taxa.