Abbott Richard J, Brochmann Christian
Harold Mitchell Building, Division of Environmental Biology, University of St Andrews, St Andrews, Fife KY16 9TH, UK.
Mol Ecol. 2003 Feb;12(2):299-313. doi: 10.1046/j.1365-294x.2003.01731.x.
A major contribution to our initial understanding of the origin, history and biogeography of the present-day arctic flora was made by Eric Hultén in his landmark book Outline of the History of Arctic and Boreal Biota during the Quarternary Period, published in 1937. Here we review recent molecular and fossil evidence that has tested some of Hultén's proposals. There is now excellent fossil, molecular and phytogeographical evidence to support Hultén's proposal that Beringia was a major northern refugium for arctic plants throughout the Quaternary. In contrast, most molecular evidence fails to support his proposal that contemporary east and west Atlantic populations of circumarctic and amphi-Atlantic species have been separated throughout the Quaternary. In fact, populations of these species from opposite sides of the Atlantic are normally genetically very similar, thus the North Atlantic does not appear to have been a strong barrier to their dispersal during the Quaternary. Hultén made no detailed proposals on mechanisms of speciation in the Arctic; however, molecular studies have confirmed that many arctic plants are allopolyploid, and some of them most probably originated during the Holocene. Recurrent formation of polyploids from differentiated diploid or more low-ploid populations provides one explanation for the intriguing taxonomic complexity of the arctic flora, also noted by Hultén. In addition, population fragmentation during glacial periods may have lead to the formation of new sibling species at the diploid level. Despite the progress made since Hultén wrote his book, there remain large gaps in our knowledge of the history of the arctic flora, especially about the origins of the founding stocks of this flora which first appeared in the Arctic at the end of the Pliocene (approximately 3 Ma). Comprehensive analyses of the molecular phylogeography of arctic taxa and their relatives together with detailed fossil studies are required to fill these gaps.
1937年，埃里克·胡尔滕（Eric Hultén）出版了具有里程碑意义的著作《第四纪北极和北方生物群历史纲要》，这对我们初步了解当今北极植物群的起源、历史和生物地理学做出了重大贡献。在此，我们回顾了近期的分子和化石证据，这些证据对胡尔滕的一些观点进行了验证。现在有出色的化石、分子和植物地理学证据支持胡尔滕的观点，即白令陆桥在整个第四纪都是北极植物的主要北方避难所。相比之下，大多数分子证据未能支持他的观点，即环北极和跨大西洋物种当代的东大西洋和西大西洋种群在整个第四纪都彼此隔离。事实上，这些物种来自大西洋两岸的种群通常在基因上非常相似，因此北大西洋在第四纪似乎并未对它们的扩散构成强大障碍。胡尔滕没有就北极地区物种形成的机制提出详细观点；然而，分子研究证实许多北极植物是异源多倍体，其中一些很可能起源于全新世。由分化的二倍体或更低倍体种群反复形成多倍体，为北极植物群令人着迷的分类学复杂性提供了一种解释，胡尔滕也曾指出这一点。此外，冰川期的种群碎片化可能导致了二倍体水平上新的姐妹物种的形成。尽管自胡尔滕撰写他的著作以来已经取得了进展，但我们对北极植物群历史的了解仍存在很大空白，尤其是关于该植物群最初在上新世末期（约300万年前）出现在北极的奠基种群的起源。需要对北极类群及其近缘物种的分子系统地理学进行综合分析，并结合详细的化石研究来填补这些空白。
