Bull. Natl. Mus. Nat. Sci., Ser. B, 39(2), pp. 61–85, May 22, 2013 Distribution of the Thelypteris japonica Complex (Thelypteridaceae) in Japan Atsushi Ebihara1,* and Narumi Nakato2 1 Department of Botany, National Museum of Nature and Science, Amakubo 4–1–1, Tsukuba, Ibaraki 305–0005, Japan 2 Narahashi 1–363, Higashiyamato-shi, Tokyo 207–0031, Japan * E-mail:
[email protected] (Received 12 February 2013; accepted 25 March 2013) Abstract The distribution of the four taxa, Thelypteris japonica forma japonica, T. japonica forma formosa, T. musashiensis and T. japonica×T. musashiensis, was reassessed by observation of spore morphology of 1984 herbarium specimens deposited in the National Museum of Nature and Science. As a result of frequent changes of identification especially between T. japonica forma formosa and T. musashiensis, the range of each taxon has been drastically updated. The hybrid was recorded in 32 prefectures in total, including newly added 25 prefectures. Key words : distribution, hybrid, spore, Thelypteris. The Thelypteris japonica complex (Thelypteri- in terms of geographical coverage. The most reli- daceae) is common understory ferns ranging able distinguishing character for the species of throughout Japan except in the Ryukyu Islands. the complex is spore morphology as demon- Japanese members of the complex were recir- strated by Nakato et al. (2004) (Fig. 2), and cumscribed by Nakato et al. (2004) based on therefore sterile specimens and/or specimens cytological and morphological characters, and with only immature spores are difficult to iden- two species, one forma and one interspecific tify. hybrid are presently accepted (Fig. 1). Nakato et al.