Shimomai, H.; Nakata, T.; Katsuhara, K. R.; Kato, S.; Ushimaru, A.; Ohmido, N.

Background and Aims Urbanization-induced environmental changes have profound effects on the geographical distribution limits in natural plant species. Polyploidization, an influential dynamic genome change, may determine survival potentials of plant species in urban environments. This study focused on the native plants, Commelina communis L. (Cc) and closely related 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 was used to determine genome size and polyploidy. Chromosome karyotyping was performed by using the 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 genome size than Ccfc. GISH results indicated that Cc possesses Ccfc and another unknown genome, suggesting allopolyploidy. Conclusions These results show that the ploidy difference affects the geographical distribution, the stomata traits, and genome size between Cc and Ccfc. In addition, GISH results indicate that Cc has Ccfc and another unknown genome, suggesting Cc is an allopolyploid and these two species of the genus Commelina are distinct. Therefore, not only polyploid but also allopolyploid contributes to Cc to 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.