The pantropical Caesalpinia group includes 225 species in 27 monophyletic genera, and the group has undergone recent phylogenetic, taxonomic and biogeographic revisions. Previous works have reported a diverse pattern of heterochromatin distribution related to ecological niche/geographic distribution, and variation in genome size also correlated with environmental variables. In order to investigate the relationship between cytogenetic and ecological traits using the Caesalpinia group as a model, new cytomolecular data (chromosome number and morphology, CMA/DAPI staining and number and position of 5S and 35S rDNA sites) for 14 species in six genera were generated. These data were analysed by phylogenetic comparative methods. All species studied have 2 n = 24 (16 M/SM + 8A), and most of them just have one pair of 5S rDNA sites and two to five pairs of 35S rDNA sites. Three heterochromatic patterns were observed on the chromosomes: (i) proximal CMA + /DAPI − bands, (ii) proximal CMA 0 /DAPI − bands and (iii) proximal CMA 0 /DAPI 0 bands. The “ Coulteria + Tara” and “ Arquita + Balsamocarpon + Erythrostemon + Pomaria” clades (except for E. gilliesii , E. hughesii and E. mexicanus ) independently showed CMA 0 /DAPI − bands associated with larger genomes and geographic distributions at higher latitudes. We statistically demonstrate that heterochromatin (CMA/DAPI intensity along the chromosome), genome size and latitude are autocorrelated in the Caesalpinia group. On the other hand, we found a non-significant correlation between genome size and amount of heterochromatin. We argue that environmental factors associated with different latitude may have played a role in contributing to the diversification of the heterochromatin in Caesalpinia group.

中文翻译：

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重新审视 Caesalpinia 组（豆科）的细胞分子进化：广泛的抽样揭示了细胞遗传学和环境变量之间的新相关性

泛热带 Caesalpinia 组包括 27 个单系属中的 225 种，该组最近经历了系统发育、分类学和生物地理学的修订。以前的工作报告了与生态位/地理分布相关的异染色质分布的多样化模式，基因组大小的变化也与环境变量相关。为研究以黄麻组为模型的细胞遗传学和生态学性状之间的关系，对6个属14个物种的新细胞分子数据（染色体数目和形态、CMA/DAPI染色以及5S和35S rDNA位点的数目和位置）进行了研究。生成。这些数据通过系统发育比较方法进行分析。研究的所有物种有 2 n = 24 (16 M/SM + 8A)，他们中的大多数只有一对 5S rDNA 位点和两到五对 35S rDNA 位点。在染色体上观察到三种异色模式：（i）近端 CMA + /DAPI - 带，（ii）近端 CMA 0 /DAPI - 带和（iii）近端 CMA 0 /DAPI 0 带。“Coulteria + Tara”和“Arquita + Balsamocarpon + Erythrostemon + Pomaria”进化枝（E. gilliesii、E. Hughhesii 和 E. mexicanus 除外）独立地显示 CMA 0 /DAPI - 带与更高纬度的更大基因组和地理分布相关. 我们在统计上证明异染色质（沿染色体的 CMA/DAPI 强度）、基因组大小和纬度在 Caesalpinia 组中是自相关的。另一方面，我们发现基因组大小与异染色质数量之间不存在显着相关性。