Allopolyploidy enhances survival advantages for urban environments in the native plant genus Commelina.

Background and aims: 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 L. (Cc) and its subspecies, C. communis f. ciliata (Masam.) Murata (Ccfc) which have different chromosome numbers (e.g. Cc: 2n = 88, Ccfc: 2n = 46). The aim is to investigate polyploidization effects on natural plant distribution in urban environments.

Methods: 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 genomic in situ hybridization (GISH) method.

Key results: Urban areas were exclusively dominated by Cc, while Cc and Ccfc coexisted in rural areas. Cc had larger and fewer stomata and more than twice the genome size than Ccfc. GISH results indicated that Cc possesses Ccfc and another unknown genome, suggesting allopolyploidy.

Conclusions: Our results show that the ploidy difference affects the geographical distribution, the 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, therefore, not only polyploidy but also an additional genome with new sets of genes and alleles contributes to Cc having enhance survival potentials in urban environments compared to 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 conduct chromosome composition in Commelina species.