Masaryk University, Faculty of Science, Department of Botany and Zoology, Kotlarska 2, Brno, Czech Republic.
Bolus Herbarium, Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch, Cape Town 7701, South Africa.
Ann Bot. 2023 Feb 7;131(1):143-156. doi: 10.1093/aob/mcac027.
It is unclear how widespread polyploidy is throughout the largest holocentric plant family - the Cyperaceae. Because of the prevalence of chromosomal fusions and fissions, which affect chromosome number but not genome size, it can be impossible to distinguish if individual plants are polyploids in holocentric lineages based on chromosome count data alone. Furthermore, it is unclear how differences in genome size and ploidy levels relate to environmental correlates within holocentric lineages, such as the Cyperaceae.
We focus our analyses on tribe Schoeneae, and more specifically the southern African clade of Schoenus. We examine broad-scale patterns of genome size evolution in tribe Schoeneae and focus more intensely on determining the prevalence of polyploidy across the southern African Schoenus by inferring ploidy level with the program ChromEvol, as well as interpreting chromosome number and genome size data. We further investigate whether there are relationships between genome size/ploidy level and environmental variables across the nutrient-poor and summer-arid Cape biodiversity hotspot.
Our results show a large increase in genome size, but not chromosome number, within Schoenus compared to other species in tribe Schoeneae. Across Schoenus, there is a positive relationship between chromosome number and genome size, and our results suggest that polyploidy is a relatively common process throughout the southern African Schoenus. At the regional scale of the Cape, we show that polyploids are more often associated with drier locations that have more variation in precipitation between dry and wet months, but these results are sensitive to the classification of ploidy level.
Polyploidy is relatively common in the southern African Schoenus, where a positive relationship is observed between chromosome number and genome size. Thus, there may be a high incidence of polyploidy in holocentric plants, whose cell division properties differ from monocentrics.
在最大的真核植物科——莎草科中，多倍体的分布情况尚不清楚。由于染色体融合和裂变的普遍存在，这些过程会影响染色体数量而不影响基因组大小，因此仅根据染色体计数数据，无法确定真核谱系中的个体植物是否为多倍体。此外，在真核谱系中，如莎草科，基因组大小和倍性水平的差异与环境相关因素之间的关系尚不清楚。
我们将分析重点放在族莎草族，更具体地说，是南部非洲莎草属的分支。我们考察了莎草族的全基因组大小演化模式，并更集中地通过 ChromEvol 程序推断南非莎草属的多倍体的普遍性，以及解释染色体数量和基因组大小数据，以确定南非莎草属的多倍体的普遍性。我们进一步研究了在营养贫乏和夏季干旱的开普生物多样性热点地区，基因组大小/倍性水平与环境变量之间是否存在关系。
与莎草族中的其他物种相比，我们的结果表明莎草属内的基因组大小有了很大的增加，但染色体数量没有增加。在整个莎草属中，染色体数量和基因组大小之间存在正相关关系，我们的结果表明多倍体在整个南非莎草属中是一个相对普遍的过程。在开普地区的区域尺度上，我们表明多倍体更常与降水变化较大的干燥地区相关，这些地区在干湿月份之间的降水差异较大，但这些结果对倍性水平的分类敏感。
在南非莎草属中，多倍体较为常见，并且观察到染色体数量与基因组大小之间存在正相关关系。因此，在真核植物中，多倍体的发生率可能较高，其细胞分裂特性与单核生物不同。
