Tropical Ecology and Evolution (TrEE) Lab, Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Bhopal, 462066, Madhya Pradesh, India.
Am J Bot. 2024 Aug;111(8):e16334. doi: 10.1002/ajb2.16334. Epub 2024 Jun 2.
Cytogenetic traits such as an organism's chromosome number and genome size are taxonomically critical as they are instrumental in defining angiosperm diversity. Variations in these traits can be traced to evolutionary processes such as polyploidization, although geographic variations across cytogenetic traits remain underexplored. In the pantropical monocot family Zingiberaceae (~1500 species), cytogenetic traits have been well documented; however, the role of these traits in shaping taxonomic diversity and biogeographic patterns of gingers is not known.
A time-calibrated Bayesian phylogenetic tree was constructed for 290 taxa covering three of the four subfamilies in Zingiberaceae. We tested models of chromosome number and genome size evolution within the family and whether lineage age, taxonomic diversity, and distributional range explain the variations in the cytogenetic traits. Tests were carried out at two taxonomic ranks: within Zingiberaceae and within genus Hedychium using correlations, generalized linear models and phylogenetic least square models.
The most frequent changes in chromosome number within Zingiberaceae were noted to be demi-polyploidization and polyploidization (57% of the time), followed by ascending dysploidy (27%). The subfamily Zingiberoideae showed descending dysploidy at its base, while Alpinioideae showed polyploidization at its internal nodes. Although chromosome counts and genome sizes did not corroborate with each other, suggesting that they are not equivalent; higher chromosome number variations and higher genome size variations were associated with higher taxonomic diversity and wider biogeographic distribution.
Within Zingiberaceae, multiple incidences of polyploidization were discovered, and cytogenetic events appear to have reduced the genome sizes and increased taxonomic diversity, distributional ranges and invasiveness.
细胞遗传学特征，如生物体的染色体数目和基因组大小，在分类学上是至关重要的，因为它们有助于定义被子植物的多样性。这些特征的变化可以追溯到进化过程，如多倍体化，尽管细胞遗传学特征的地理变化仍未得到充分探索。在泛热带单子叶植物姜科（约 1500 种）中，细胞遗传学特征得到了很好的记录；然而，这些特征在塑造姜科植物的分类多样性和生物地理模式中的作用尚不清楚。
构建了一个包含姜科四个亚科中的三个的 290 个分类单元的时间校准贝叶斯系统发育树。我们测试了该科内染色体数目和基因组大小进化的模型，以及谱系年龄、分类多样性和分布范围是否解释了细胞遗传学特征的变化。在两个分类学等级上进行了测试：在姜科内和在 Hedychium 属内，使用相关性、广义线性模型和系统发育最小二乘法模型进行了测试。
在姜科内，染色体数目的最常见变化是半多倍体化和多倍体化（约 57%的时间），其次是上升的非整倍体化（约 27%）。姜亚科在其基部表现出下降的非整倍体化，而姜花亚科在其内部节点表现出多倍体化。尽管染色体计数和基因组大小不一致，表明它们并不等同；较高的染色体数目变化和较高的基因组大小变化与较高的分类多样性和较宽的生物地理分布有关。
在姜科内，发现了多次多倍体化事件，细胞遗传学事件似乎降低了基因组大小，增加了分类多样性、分布范围和入侵性。
