In Taiwan the two Taiwan endemic species, Rhododendron pseudochrysanthum and R. hyperythrum , are sympatric in the northeastern and central alpine ridges. A natural hybrid putatively originated from these two species was recognized based on field observations and morphological studies. In its leaf-shape, the hybrid resembles the putative parents but with the lower surface being gray to brownish indumentum, which is intermediate between those of the former parent (sparse gray) and the latter (dense rust-brown). Six additional taxa represent other three subgenera of Rhododendron were also sampled, and nuclear ITS as well as chloroplast maturase K (cp matK) sequences were employed to examine relationships between the hybrid and its proposed parents. The ITS-based analyses strongly supported that the hybrid originates from interbreed of parental populations in Mt. Nanhu, and the hybrid origin is likely very recent. Indels found in the ITS provided reliable information as to the possible parental parent. We are in the process of assembling the cp matK data. A more thorough assessment as to the maternal and parental parents will be presented.

Key words: hybrid origin, ITS, matK, Phylogeny, Rhododendron