Department of Plant Biology, Cornell University, Ithaca, NY 14853, USA.
New Phytol. 2010 Apr;186(1):73-85. doi: 10.1111/j.1469-8137.2009.03118.x. Epub 2009 Dec 16.
is a widespread speciation mechanism, particularly in plants. Estimating the time of origin of polyploid species is important for understanding issues such as gene loss and changes in regulation and expression among homoeologous copies that coexist in a single genome owing to polyploidy. Polyploid species can originate in various ways; the effects of mode of origin, genetic system, and sampling on estimates of the age of polyploid origin using distances between alleles of polyploids and their diploid progenitors, or between homoeologous loci in a polyploid genome, are explored. Even in the simplest cases, simulations confirm that different loci are expected to give very different estimates of the date of origin. The time of polyploid origin is at least as old as the time estimated from comparison of an allele sampled from the polyploid with the most closely related allele in the diploid progenitor. The polyploidy literature often does not make clear the longstanding observation that the divergence of homoeologous copies in an allopolyploid tracks the divergence of diploid species, not the origin of the polyploid. Estimating the date of origin of a polyploid is difficult, and in some circumstances impossible. Skepticism about dates of polyploid origins is clearly warranted.
是一种广泛存在的物种形成机制，特别是在植物中。估计多倍体物种的起源时间对于理解由于多倍体而在单个基因组中共存的同源拷贝的基因丢失和调控以及表达变化等问题非常重要。多倍体物种可以通过多种方式起源；起源方式、遗传系统和采样对使用多倍体和其二倍体祖先之间的等位基因之间的距离或多倍体基因组中的同源基因座之间的距离来估计多倍体起源年龄的影响进行了探讨。即使在最简单的情况下，模拟也证实不同的基因座预计会给出多倍体起源日期的非常不同的估计值。多倍体起源的时间至少与从多倍体中取样的等位基因与二倍体祖先中最相关的等位基因进行比较所估计的时间一样长。多倍体文献通常没有明确指出一个长期存在的观察结果，即异源多倍体的同源拷贝的分化与二倍体物种的分化相吻合，而不是与多倍体的起源相吻合。估计多倍体的起源日期很困难，在某些情况下甚至不可能。对多倍体起源日期的怀疑显然是有道理的。
