Stable allopolyploidy in a hybrid zone within the Matsukawaura Lagoon (Japan) between Neopyropia yezoensis and Neopyropia tenera (Bangiales, Rhodophyta) and its relevance to speciation mechanisms and crop improvement

Abstract To confirm the distribution of the allopolyploid and ancestral species in the Matsukawaura Lagoon in a hybrid zone between Neopyropia yezoensis and Neopyropia tenera , molecular marker analyses and culture experiments were performed using collected blades. All the blades examined, except for one blade identified as N . tenera , exhibited nuclear genotypes of both species, but only the chloroplast haplotype of N . yezoensis . In addition, four conchocelis strains were isolated from each of the blades, and they contained genotypes of both N . yezoensis and N . tenera ; a conchocelis strain from the sole N . tenera blade was also isolated. Using the conchocelis strains, F 1 blades that were produced from archeospores were obtained under laboratory culture and examined by nuclear DNA markers. These results indicated that the collected blades and the examined F 1 blades, except for the single N . tenera blade, were allodiploids and that the four conchocelis strains could be allotetraploids derived from interspecific hybridization between N . yezoensis as the maternal strain and N . tenera as the paternal strain. Therefore, most of the Neopyropia blades growing in the Matsukawaura Lagoon are presumed to be from allopolyploid lineages derived from interspecific hybridization. Furthermore, a growth comparison between the allopolyploid strain and the N . tenera strain was carried out under identical culture conditions. The rate of increase in blade length was significantly higher in the allopolyploid hybrid than in the pure N . tenera . The results suggest that further exploration of allopolyploidy in the potential hybrid zones will be needed not only for the investigation of speciation mechanisms in the bladed Bangiales but also for the genetic improvement of the marine crop.