Aichryson disjunct

Ito, Takuro, Nakamura, Koh, Park, Chan-Ho, Song, Gwan-Pil, Maeda, Ayako, Tanabe, Yuki & Kokubugata, Goro, 2014, Nuclear and plastid DNA data confirm that Sedum tosaense (Crassulaceae) has a disjunct distribution between Pacific mainland Japan and Jeju Island, Korea, Phytotaxa 177 (4), pp. 221-230 : 227

A disjunct Sedum tosaense distribution pattern between Kochi and Jeju Island

Our molecular analysis revealed that Sedum tosaense from Kochi and Jeju Island belonged to a strongly supported clade (clade IA in Fig. 3 ). This concurs with the report by Song et al. (2004), who found S. tosaense on Jeju Island. Therefore, we have shown a disjunct distribution pattern for S. tosaense between the two regions through an analysis of the ITS and partial trnLF sequences.

Plants species that occur on both Jeju Island and in most regions of the Japanese mainland have been reported previously; e. g., Stellaria sessiliflora Y. Yabe (1903: 194 ; Caryophyllaceae ) ( Akiyama 2006), Lysimachia acroadenia Maxim. (1868: 70; Primulaceae ) ( Yamazaki 1993), and Carpesium glossophyllum Maxim. (1874: 475; Asteraceae ) ( Koyama 1995). Some species on Jeju Island occur in restricted western parts of the Japanese mainland, such as the Kyushu District, which is the Japanese territory closest to Jeju ( Fig. 1 ); e. g., Adenophora tashiroi (Makino et Nakai) Makino et Nakai (1911: 66 ; Campanulaceae ) ( Shimizu 1993). However, ours is the first report of a disjunct distribution between Kochi, a Japanese region bordering the Pacific Ocean ( Fig. 1 ), and Jeju Island.

Although our molecular analyses clearly show that S. tosaense from Kochi and Jeju Island were phylogenetically closest among Asian Sedum species we investigated, the taxonomic affinity of the Kochi and Jeju populations remains unclear. Plants identified as S. tosaense were reported from Mt. Lin’an Xian area, situated in the northern part of Zhejiang Province, China ( Fu & Ohba 2001), but the taxonomic status of the Chinese plants is not clear, because Fu & Rao (1998) treated them as a different subspecies, S. tosaense subsp. sinense Fu & Rao (1998: 121) , and stated that this subspecies was morphologically different from var. tosaense in having aggregated leaves at the upper part of the sterile stem. For a comprehensive, global understanding of the taxonomic status of the species, morphological comparisons should be performed on collections from all three countries; the comparisons should include floral traits. Even if the Jeju and Zhejiang populations were subsequently shown to be taxonomically independent of S. tosaense in the Shikoku District of Japan, we have nevertheless shown that there is a disjunct distribution between Kochi and Jeju Island at the infraspecific level.

Figures

FIGURE 1. Habit of Sedum tosaense. A. Plant in Kochi Prefecture, Japan (8 December 2012). B. Plant on Jeju Island, Korea (6 July 2013). Bars = 3 cm.

FIGURE 3. Maximum clade credibility tree using multispecies coalescent analysis based on ITS and cpDNA data.The numerals beside branches are Bayesian posterior probabilities (PP) (upper). Clade depth indicates the mean nodal age (million years) (lower) and nodes with PP ≥ 0.90 are annotated with the 95% highest posterior density intervals for node ages by bars.