Does hybridization drive the transition to asexuality in diploid Boechera?

Gametophytic apomixis is a common form of asexual reproduction in plants. Virtually all gametophytic apomicts are polyploids, and some view polyploidy as a prerequisite for the transition to apomixis. However, any causal link between apomixis and polyploidy is complicated by the fact that most apomictic polyploids are allopolyploids, leading some to speculate that hybridization, rather than polyploidy, enables apomixis. Diploid apomixis presents a rare opportunity to isolate the role of hybridization, and a number of diploid apomicts have been documented in the genus Boechera (Brassicaceae). Here we present the results of a microsatellite study of 1393 morphologically and geographically diverse diploid individuals, evaluating the hypothesis that diploid Boechera apomicts are hybrids. This genus-wide dataset was made possible by the applicability of a core set of microsatellite loci in 69 of the 70 diploid Boechera species and by our ability to successfully genotype herbarium specimens o...配子体无融合生殖（Gametophytic apomixis）是植物中一类常见的无性生殖方式。几乎所有配子体无融合生殖物种均为多倍体，部分学者将多倍性视为向无融合生殖过渡的必要前提。然而，多数无融合生殖多倍体均为异源多倍体（allopolyploids），这一事实使得无融合生殖与多倍性之间的因果关联变得复杂，进而有学者推测是杂交而非多倍性促成了无融合生殖的发生。二倍体无融合生殖为明确杂交在无融合生殖中的具体作用提供了难得的研究契机，目前在十字花科（Brassicaceae）Boechera属中已记录有多种二倍体无融合生殖物种。本研究针对1393份形态与地理分布均具有多样性的二倍体个体开展微卫星（microsatellite）分析，旨在验证‘Boechera属二倍体无融合生殖物种均为杂交起源’这一假说。本次覆盖全属的数据集得以完成，得益于一套核心微卫星位点可适用于70个Boechera属二倍体物种中的69个，同时得益于我们可成功对标本馆标本进行基因分型……