Polyploidy in arctic plants
Polyploidy in arctic plants
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DOI：
10.1111/j.1095-8312.2004.00337.x
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发表时间：
2004-08-01
影响因子：
1.9
通讯作者：
Elven, R
中科院分区：
文献类型：
--
作者：
Brochmann, C;Brysting, AK;Elven, R
北极是研究多倍体的极佳模式系统。它是地球上多倍体最丰富的地区之一，特别是高水平和最近进化的多倍体。在此，我们基于对北极植物区系的最新分析，重新提出了关于北极多倍体的假说，并回顾了最近的分子、细胞学和生殖研究。在北极地区，多倍体的频率和水平向北强烈增加。我们没有发现北极植物区系的多倍性和冰川化程度之间的明确联系，因为北极植物区系包含许多分布广泛的物种。然而，对于分布有限的北极专家分类群来说，二倍体在柏林地区的频率要比在冰川严重的大西洋地区高得多，该地区在上一次冰河时代基本上没有冰川。这一结果支持了多倍体在冰川消融后比二倍体更成功地定植的假说。在不同的时间和空间尺度上，北极多倍体的反复形成有丰富的分子证据。给出了末次冰期后形成的低水平多倍体以及在整个第四纪反复和连续更多的高水平多倍化的例子。反复的多倍体起源，然后是倍性水平内和倍性水平之间的杂交，为北极植物区系的分类复杂性提供了一个主要解释。在最近冰川消融的斯瓦尔巴群岛上，大多数物种主要是自花授粉或克隆。到目前为止，所有检测到的斯瓦尔巴群岛多倍体都是遗传异源多倍体，在同工酶座位上具有固定的杂合度。从二倍体到高水平的多倍体，65个分类群的杂合度水平显著增加。在北极地区，有证据表明，在二倍体分类物种中有许多最近进化的兄弟物种。在二倍体水平上的跨越障碍的快速进化促进了异源多倍体的形成。我们的结论是，北极多倍体的进化成功可能是基于它们的固定杂合子基因组，这种基因组缓冲了近亲繁殖和在气候剧烈变化期间的遗传漂移。(C)2004年伦敦林尼安协会。
The Arctic is an excellent model system for the study of polyploidy. It is one the Earth's most polyploid-rich areas, in particular of high-level and recently evolved polyploids. Here we re-address previous hypotheses on arctic polyploidy based on a new analysis of the circumarctic flora, and review recent molecular, cytological and reproductive studies. The frequency and level of polyploidy strongly increase northwards within the Arctic. We found no clear-cut association between polyploidy and the degree of glaciation for the arctic flora as a whole, which contains many widespread species. However, for 'arctic specialist' taxa with restricted distributions, the frequency of diploids is much higher in the Beringian area, which remained largely unglaciated during the last ice age, than in the heavily glaciated Atlantic area. This result supports the hypothesis that polyploids are more successful than diploids in colonizing after deglaciation. There is abundant molecular evidence for recurrent formation of arctic polyploids at different scales in time and space. Examples are given of low-level polyploids formed after the last glaciation and of repeated and successively more high-level polyploidizations throughout the Quaternary. Recurrent polyploid origins, followed by interbreeding within and across ploidal levels, provide a major explanation for the taxonomic complexity of the arctic flora. In the well-studied, recently deglaciated archipelago of Svalbard, most species are mainly self-fertilizing or clonal. All Svalbard polyploids examined so far are genetic allopolyploids with fixed heterozygosity at isozyme loci. The level of heterozygosity in 65 taxa increases dramatically from diploids to high-level polyploids. In the circumarctic area, there is evidence for numerous recently evolved sibling species within diploid taxonomic species. Rapid evolution of crossing barriers at the diploid level promotes further diversification after expansion from different refugia, and may provide new raw materials for allopolyploid formation. We conclude that the evolutionary success of polyploids in the Arctic may be based on their fixed-heterozygous genomes, which buffer against inbreeding and genetic drift through periods of dramatic climate change. (C) 2004 The Linnean Society of London.