Escudero Marcial, Hahn Marlene, Brown Bethany H, Lueders Kate, Hipp Andrew L
The Morton Arboretum, 4100 Illinois Route 53, Lisle, Illinois 60532 USA Department of Botany, The Field Museum of Natural History, 1400 S. Lake Shore Drive, Chicago, Illinois 60605 USA Department of Plant Biology and Ecology, University of Seville, Reina Mercedes sn 41010 Seville, Spain.
The Morton Arboretum, 4100 Illinois Route 53, Lisle, Illinois 60532 USA.
Am J Bot. 2016 Aug;103(8):1529-36. doi: 10.3732/ajb.1600051. Epub 2016 Aug 24.
Understanding the drivers of speciation is a central task of evolutionary biology. Chromosomal rearrangements are known to play an important role in species diversification, but the role of rearrangements of holocentric chromosomes-chromosomes without localized centromeres-is poorly understood.
We made numerous artificial crosses between Carex scoparia individuals of different diploid chromosome numbers and, for comparison, between individuals of the same chromosome number. We studied chromosome pairing and chromosomal rearrangements in the F1 individuals using light microscopy. We then estimated germination rates as a function of geographic distance, genetic distance, chromosome number differences in parents, and pairing irregularities in F1 individuals, using generalized least squares to fit alternative regression models.
The most informative predictors of germination rates in the F1 generation are chromosome number differences and minimum number of chromosome pairing irregularities in the F1 individuals. Genetic and geographic distances between parents are not significant predictors.
Holocentric chromosomal rearrangements play an important role in postzygotic reproductive isolation in Carex through F1 hybrid inviability and sterility. Hybrid dysfunction seems to be a suitable model for chromosomal speciation when there are several chromosomal rearrangements between parents. However, we have not tested the hypothesis that genome rearrangements may also play an important role in suppressing recombination between cytogenetically divergent populations.
理解物种形成的驱动因素是进化生物学的核心任务。已知染色体重排在物种多样化中发挥重要作用，但全着丝粒染色体（即没有局部着丝粒的染色体）的重排作用却鲜为人知。
我们在不同二倍体染色体数目的苔草个体之间进行了大量人工杂交，并作为比较，也在相同染色体数目的个体之间进行了杂交。我们使用光学显微镜研究了F1代个体中的染色体配对和染色体重排。然后，我们使用广义最小二乘法拟合替代回归模型，将发芽率估计为地理距离、遗传距离、亲本染色体数差异以及F1代个体中配对不规则性的函数。
F1代发芽率最具信息量的预测因子是染色体数差异和F1代个体中染色体配对不规则的最小数量。亲本之间的遗传距离和地理距离不是显著的预测因子。
全着丝粒染色体重排在苔草的合子后生殖隔离中通过F1杂种的 inviability 和不育发挥重要作用。当亲本之间存在几种染色体重排时，杂种功能障碍似乎是染色体物种形成的合适模型。然而，我们尚未检验基因组重排在抑制细胞遗传学上不同种群之间的重组中也可能发挥重要作用这一假设。
