Nuphar × saijoensis is a species of rhizomatous aquatic plant endemic to Japan. It is a natural hybrid of Nuphar japonica and Nuphar pumila,USDA, Agricultural Research Service, National Plant Germplasm System. 2024. Germplasm Resources Information Network (GRIN Taxonomy). National Germplasm Resources Laboratory, Beltsville, Maryland. URL: https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomydetail?id=420213. Accessed 27 January 2024. or Nuphar japonica and Nuphar pumila subsp. oguraensis.植物地理, & 分類研究. (2002). "Seed production and germination in endangered Nuphar (Nymphaeaceae) of western Japan." Journal of Phytogeography and Taxonomy, 50, 35-40.Kondo, T., Watanabe, S., Shiga, T., & Isagi, Y. (2016). "Microsatellite markers for Nuphar japonica (Nymphaeaceae), an aquatic plant in the agricultural ecosystem of Japan." Applications in Plant Sciences, 4(12), 1600082.
Description Generative characteristics The anthers are strongly recurved.
Reproduction Generative reproduction It is fertile, but only very few, mostly unviable seeds are produced with an average of 29 seeds per fruit.
Taxonomy Publication It was first described as the variety Nuphar japonica var. saijoensis Shimoda by Michiko Shimoda in 1991. Later, it was treated as the natural hybrid Nuphar × saijoensis (Shimoda) Padgett & Shimoda published by Donald Jay Padgett and Michiko Shimoda in 2002.
Type specimen The type specimen was collected by Michiko Shimoda in Higashi-hiroshima City, Hiroshima Prefecture, Japan on the 27th of June 1989. Natural hybridisation Different sources list different species involved, depending on the recognition of Nuphar taxa. Nuphar japonica is listed as a parental species in all sources. The other parental species is either listed as Nuphar oguraensis (syn. Nuphar pumila subsp. oguraensis),Shiga, T., & Kadono, Y. (2007). Natural hybridization of the two Nuphar species in northern Japan: Homoploid hybrid speciation in progress?. Aquatic botany, 86(2), 123-131. or as Nuphar pumila. In the original publication the second parental species Nuphar oguraensis is listed as Nuphar pumila subsp. oguraensis.
Conservation It is endangered.
Ecology Habitat It only occurs in aquatic habitats, such as irrigation ponds, of the Saijo Basin, western Japan.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.Takashi Shiga. (2007). "A systematic study of Nuphar (Nymphaeaceae) in Japan with special reference to the role of hybridization [Doctoral Dissertation."] Kobe University.
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