Shimomai Hina, Taichi Nakata, Katsuhara Koki R, Kato Seiji, Ushimaru Atushi, Ohmido Nobuko
Graduate School of Human Development and Environment, Kobe University, 657-8501, Kobe, Japan.
Graduate School of Environmental and Life Science, Okayama University, Okayama, Okayama 700-8530, Japan.
Ann Bot. 2024 Dec 31;134(6):1055-1066. doi: 10.1093/aob/mcae141.
Urbanization-induced environmental changes affect the geographical distribution of natural plant species. This study focused on how polyploidization, a dynamic genome change, influences the survival and distribution of Commelina communis (Cc) and its subspecies C. communis f. ciliata (Ccfc), which have variable chromosome numbers (e.g. Cc, 2n = 88 for Cc; Ccfc, 2n = 46 for Ccfc). The aim was to investigate polyploidization effects on natural plant distribution in urban environments.
The geographical distribution across urban-rural gradients was investigated at a total of 218 sites in Japan. Stomata size and density were measured and compared between Cc and Ccfc. Flow cytometry determined genome size and polyploidy. Chromosome karyotyping was performed using the genomic in situ hybridization (GISH) method.
Urban areas were exclusively dominated by Cc, while Cc and Ccfc coexisted in rural areas. Cc had larger and fewer stomata and a genome size more than twice that of Ccfc. GISH results indicated that Cc possesses Ccfc and another unknown genome, suggesting allopolyploidy.
Our results show that the ploidy difference affects the geographical distribution, stomata traits and genome size between two distinct taxa in the genus Commelina, C. communis as a neo-tetraploid and C. communis f. ciliata, the diploid. Cc is an allopolyploid and is therefore not only polyploidy but also has an additional genome that provides new sets of genes and alleles, contributing to Cc having enhanced survival potentials in urban environments compared with Ccfc. This is the first investigation to clarify the distribution difference related to urban environments, the difference in stomata traits and genome size, and to study chromosome composition in Commelina species.
城市化引发的环境变化影响着天然植物物种的地理分布。本研究聚焦于多倍体化这一动态基因组变化如何影响鸭跖草及其亚种睫毛鸭跖草的生存与分布，它们具有可变的染色体数目（例如，鸭跖草2n = 88；睫毛鸭跖草2n = 46）。目的是探究多倍体化对城市环境中天然植物分布的影响。
在日本总共218个地点调查了城乡梯度上的地理分布。测量并比较了鸭跖草和睫毛鸭跖草的气孔大小和密度。采用流式细胞术测定基因组大小和多倍体情况。使用基因组原位杂交（GISH）方法进行染色体核型分析。
城市地区仅由鸭跖草占据，而鸭跖草和睫毛鸭跖草在农村地区共存。鸭跖草的气孔更大、数量更少，且基因组大小是睫毛鸭跖草的两倍多。GISH结果表明，鸭跖草拥有睫毛鸭跖草和另一个未知基因组，提示其为异源多倍体。
我们的结果表明，倍性差异影响鸭跖草属中两个不同分类群之间的地理分布、气孔特征和基因组大小，鸭跖草为新四倍体，睫毛鸭跖草为二倍体。鸭跖草是异源多倍体，因此不仅具有多倍体特征，还拥有额外的基因组，提供了新的基因和等位基因组合，这使得鸭跖草与睫毛鸭跖草相比，在城市环境中具有更强的生存潜力。这是首次阐明与城市环境相关的分布差异、气孔特征和基因组大小差异，并研究鸭跖草属物种染色体组成的调查。
