Morphology and phylogenetics of two holoparasitic plants, Balanophora japonica and Balanophora yakushimensis (Balanophoraceae), and their hosts in Taiwan and Japan.

Balanophora japonica and B. yakushimensis are two putatively agamospermic taxa previously reported from southern Japan. Their inflorescences superficially represent those of B. laxiflora and B. fungosa. In this study we confirmed their presence in Taiwan by morphological and phylogenetic analysis using nuclear 18S rDNA and nrITS sequences with related taxa. B. japonica, B. yakushimensis, and B. laxiflora formed a well-supported clade that is distinct from other Balanophora. All three taxa also show considerable differences on morphological and nucleotide sequence differences, therefore the name of B. yakushimensis is retained. The results provide new insights on the intrageneric classification of Balanophora and suggest the positioning of female flowers should be down-weighted. We also successfully identify the hosts of B. japonica and B. yakushimensis by amplifying chloroplast matK sequences from the connected root tissues. The results showed that B. japonica parasitizes on Symplocos species, and that B. yakushimensis parasitizes on Distylium racemosum in Japan and Schima superba in Taiwan's population.