Shiga T.and Y. Kadono, 2004. Morphological variation and classification of Nuphar with special reference to the populations in central to western Japan. Acta Phytotaxonomica et Geobotanica. APG 55(2): 107-117.
Abstract
Morphological variations of a total of 52 populations of Nuphar japonica DC., N. subintegerrima (Casp.) Makino, N. oguraensis Miki and unidentified intermediate plants were investigated in the scope of a revision of Japanese Nuphar, Nymphaeaceae. The phenogram of cluster analysis based on 15 morphological characters revealed five cluster groups (A-E). Clusters A, C and E had some remarkable characters and corresponded well to the description of N. japonica, N. oguraensis and N. subintegerrima sensu stricto, respectively. On the other hand, Clusters B and D showed intermediate values in most of their characters. It was concluded that these intermediate plants, which had usually been identified as N. subintegerrima, were not conspecific with N. subintegerrima s. s. and there were two different intermediate groups in central to western Japan. Morphological relationships suggested that the two intermediate groups were of hybrid origin between N. japonica and N. oguraensis and between N. japonica and N. subintegerrima, respectively. As a consequence of the present study it was proved that the populations of N. subintegerrima s. s. was very limited in number and in its distribution area and truly one of the most endangered plants in Japan.
Key words:
cluster analysis, hybridization, intermediate forms, morphological variations, Nuphar japonica, Nuphar oguraensis, Nuphar subintegerrima, phenetic relationships