To understand the diversity of Machilus (Lauraceae) in the Bonin Islands, we investigated genetic structure and several eco-geographical traits of 17 local populations, with using six nuclear microsatellite markers and observation of habitat differences and flowering phenology. As a results, we defined three groups in M. boninensis, two groups in M. kobu, and one group in M. pseudokobu. Populations of each species were genetically differentiated between Chichijima and Hahajima in the Bonin Islands. On Chichijima, populations of M. boninensis were further genetically differentiated between habitats, i.e., dry scrub and mesic forest. Within Chichijima and Hahajima populations, differences in sharp flowering peaks were observed among the groups; but populations of M. boninensis in mesic forests had a longer flowering period with multiple peaks. According to our observations, not only isolation by distance between the islands, but also ecological selection in response to dry scrub often formed on boninite soils, which result in similar physiological traits as in plants on serpentinite soils. This appears to drive diversification in Machilus in the Bonin Islands. The long flowering periods may have evolved as a successful adaptative to growing in the subcanopy layer or interior of the mesic forests.

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Calex filipes (Cyperaceae) and its closely related species, which we tentatively refer to as the C. filipes complex, are greatly diverse morphologically. The closely allied species have often been included within C. filipes where they have been treated by as many as seven infraspecific taxa at the rank of variety. To better determin the taxonomic distinctness of the individual species and infraspecific taxa, we undertook molecular phylogenetic analyses of individuals of the C. filipes complex using the plastid DNA regions atpB–rbcL, rpl16–rpl16–rps3, rps16, matK, and trnL–trnL–trnF and nuclear DNA regions ITS and ETS. We compared the morphology of as many individuals as possible and determined the somatic chromosome number of some individuals to supplement missing information. It was concluded that the C. filipes complex comprises ten species, two varieties and one hybrid, i.e. C. arisanensis, C. curtispica, C. egena, C. filipes var. filipes, C. filipes var. tremula, C. kujuzana, C. ×kurogii, C. kuzakaiensis, C. rouyana var. arakiana, C. rouyana var. rouyana, C. sohayakiensis, C. sparsinux and C. vaniotii. A diagnostic key to separate them, based on morphology, and chromosome numbers are presented. Two new species, C. curtispica and C. sohayakiensis and one new hybrid, C. ×kurogii, are described. The origin of the hybrid isalso discussed.

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Cypripedium macranthos is a polymorphic species with wide variation in vegetative traits, flower color and morphology. For the future infraspecific taxonomy of C. macranthos s. lat., I quantitatively clarified the variation of those traits in C. macranthos var. rebunense and var. macranthos on Rebun Island, Hokkaido, Japan. A quantitative analysis of flower color using the L*a*b* color system revealed distinct differences between the pale cream flowers of var. rebunense and the purplish pink flowers of var. macranthos. However, especially in the measurements of a* and b*, the flowers of var. rebunense showed wide variation (from white or pale cream to yellow, including greenish yellow). Even on Rebun Island alone, C. macranthos s. lat. showed a wide range of variation in outer morphological traits. It is not possible to clearly discriminate between var. rebunense and var. macranthos by vegetative and morphological floral traits, only in the difference in color of flowers. However, the ratio of petal length to width in var. rebunense tended to be slightly smaller than for var. macranthos. Within var. rebunense on Rebun Island, the southern Rebuntaki population showed a slight tendency toward smaller dimensions in vegetative and floral morphological traits than in the other two northern populations. Special attention should be paid to the southern part in the protection of C. macranthos var. rebunense on Rebun Island.

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The present study documents the first record of Thrixspermum annamense (Orchidaceae) from Iriomote Island, Ryukyu Islands, Japan, expanding its known distribution beyond Vietnam, Thailand, Taiwan, China, and Malaysia. While the morphologically similar taxon T. fantasticum is present on the island, it can be distinguished from T. fantasticum by its somewhat narrower and more rigid leaves, slightly narrower sepals, densely hairy midlobe of the lip, and the absence of two horn-like appendages at the base of the midlobe. A detailed morphological analysis also revealed that the plants discovered on Iriomote Island closely resemble T. annamense from Taiwan but show consistent morphological and molecular distinctions from T. annamense from Vietnam, the type locality. Despite those differences, the high similarity in gross morphology and most lip structures of the plants from Japan, Taiwan, and Vietnam indicates that they all belong to T. annamense at the species level. Consequently, considering the genetic and morphological differences, we propose resurrecting the name T. devolianum, originally described from Taiwan, and reclassifying it as a variety of T. annamense (T. annamense var. devolianum). A neotype for T. devolianum is also designated.

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Hymenophyllum pilosissimum C. Chr. (Hymenophyllaceae), recently discovered on Iriomote Island, is reported for the first time in Japan.

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Boesenbergia albomaculata S. Q. Tong (Zingiberaceae) is reported for the first time from India. It occurs in tropical evergreen forests in the transitional zone between the Eastern Himalaya and the Indo-Burma Biodiversity Hotspot.

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