Natural hybridization and the imperiled Nuphar of western Japan

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Ponds in the Saijo Basin of western Japan contain three Nuphar taxa, two of which are threatened. It has been proposed previously that the rarest of the three, hitherto Nuphar japonica var. saijoensis, may have originated from natural hybridization between N. japonica and Nuphar pumila subsp. oguraensis. To test this hypothesis, we conducted morphological analyses, pollen and seed fertility tests, and a RAPD analysis of all three pond-lilies. Individuals of the putative hybrid exhibit intermediate morphology, reduced pollen and seed viability, and genetic additivity in comparison to the other species. The putative hybrid is also limited geographically to an area of parental sympatry. Our findings support the hybrid origin of N. japonica var. saijoensis, which we recognize nomenclaturally as Nuphar×saijoensis. Loss and degradation of habitat due to urbanization is a major threat to the survival of this taxon.

Original Citation

Padgett D.J., Shimoda M., Horky L.A., Les D.H. (2002). Natural hybridization and the imperiled Nuphar of western Japan. Aquatic Botany, 72(2), 161-174. https://doi.org/10.1016/S0304-3770(01)00223-6