Data from: Chromosomes tell half of the story: the correlation between karyotype rearrangements and genetic diversity in sedges, a group with holocentric chromosomes

Chromosome rearrangements may affect the rate and patterns of gene flow within species, through reduced fitness of structural heterozygotes or by reducing recombination rates in rearranged areas of the genome. While the effects of chromosome rearrangements on gene flow have been studied in a wide range of organisms with monocentric chromosomes, the effects of rearrangements in holocentric chromosomes—chromosomes in which centromeric activity is distributed along the length of the chromosome—have not. We collected chromosome number and molecular genetic data in Carex scoparia, an eastern North American plant species with holocentric chromosomes and highly variable karyotype (2n = 56–70). There are no deep genetic breaks within C. scoparia that would suggest cryptic species differentiation. However, genetic distance between individuals is positively correlated with chromosome number difference and geographic distance. A positive correlation is also found between chromosome number and genetic distance in the western North American C. pachystachya (2n = 74–81). These findings suggest that geographic distance and the number of karyotype rearrangements separating populations affect the rate of gene flow between those populations. This is the first study to quantify the effects of holocentric chromosome rearrangements on the partitioning of intraspecific genetic variance.染色体重排（chromosome rearrangements）可通过降低结构杂合子的适合度（fitness），或降低基因组重排区域的重组速率（recombination rate），影响物种内的基因流（gene flow）速率与模式。尽管学界已针对单着丝粒染色体（monocentric chromosomes）类群广泛开展了染色体重排对基因流影响的相关研究，但针对全着丝粒染色体（holocentric chromosomes）——即着丝粒活性沿染色体全长分布的染色体——重排的相关研究仍付阙如。我们针对北美东部的全着丝粒植物帚状薹草（Carex scoparia）收集了染色体数目与分子遗传数据，该物种核型（karyotype）变异极强，染色体数目范围为2n=56~70。帚状薹草种群内不存在可指示隐存物种分化的深度遗传断点。不过，个体间的遗传距离与染色体数目差异及地理距离均呈显著正相关。在北美西部的厚穗薹草（Carex pachystachya，2n=74~81）中，同样观测到染色体数目与遗传距离呈正相关的现象。上述结果表明，地理距离以及分隔种群的核型重排数目，会影响种群间的基因流速率。本研究首次量化了全着丝粒染色体重排对种内遗传变异（intraspecific genetic variance）分配的影响。