Notes on Ptilidium californicum (Ptilidiaceae) in Japan

Abstract

  Ptilidium californicum (Austin) Underw. & O.F.Cook has been recognized as a member of Ptilidium Nees in Japan since its first discovery in 1951. However, recent molecular phylogenetic study doubted the occurrence of the species in Japan, suggesting that the Japanese P. californicum may be a poorly development phase of P. pulcherrimum (Weber) Vain. To clarify the taxonomic identity of Japanese plants, molecular phylogenetic analyses and morphological examination were carried out. The Japanese materials identified as P. californicum were clearly resolved in the P. californicum clade consisting of North American samples. Morphological examination confirmed that underleaf shape could be a stable taxonomic character to distinguish P. californicum from P. pulcherrimum, even in poorly developed plants. Therefore, we accept P. californicum as a member of Japanese bryoflora. A revised key to the species of Ptilidium in Japan is provided.