Published Papers - NAIKI Akiyo

A provisional list of alien plant species on Iriomote Island, Okinawa, Japan

Yui KAJITA, Koji YONEKURA, Hironori TOYAMA, Kensei AKAI, Masaharu AMANO, Atsushi ABE, Takuto SHITARA, Takenori YAMAMOTO, Yukiko SAITO, Masatsugu YOKOTA, Akiyo NAIKI

Bulletin of the Osaka Museum of Natural History   76   125 - 141   2022.03 [ Peer Review Accepted ]

Type of publication: Research paper (bulletin of university, research institution)

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Multiple origins of two Ochrosia (Apocynaceae) species endemic to the Bonin (Ogasawara) Islands.

Noda H, Nishimura A, Kato H, Naiki A, Xiao W, Martinez M, Marutani M, McConnell J, Takayama K

Molecular phylogenetics and evolution ( Molecular Phylogenetics and Evolution )  171   107455 - 107455   2022.03 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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The genus, Ochrosia, is widely distributed from the West Indian Ocean throughout tropical Asia to the Middle Southern Pacific region. Ochrosia comprises many island-endemic species, suggesting that long-distance dispersal and isolation after migration are key factors for clarifying the diversification process. However, the phylogeny and biogeography of endemic Ochrosia species have not been evaluated well due to the difficulty of adequate sampling from the entire distribution range of the genus. In this study, we focused on two Ochrosia species endemic to the Bonin (Ogasawara) Islands in the northwest Pacific. The Bonin Islands are of volcanic origins and consist of two islands groups, the Ogasawara and Volcano Islands groups, approximately 300 km apart. Ochrosia nakaiana is endemic to the Ogasawara Islands group, whereas O. hexandra is endemic to the Volcano Islands group. To elucidate the phylogenetic positions of these two endemic Ochrosia species, we conducted molecular phylogenetic studies with dating and biogeographic analyses including other Ochrosia species. The phylogenetic trees showed that the two endemic species had distinct origins; O. nakaiana was closely related to O. oppositifolia and O. iwasakiana, whereas O. hexandra was related to O. mariannensis. Based on the chloroplast DNA phylogeny, the genus, Ochrosia, divided into two major lineages 36.6 million years ago. Further, the two endemic species of the Bonin Islands were independently derived approximately 1-2 million years ago. Ochrosia nakaiana originated from the Southeast Asia, New Caledonia, or other Pacific Islands, while O. hexandra derived from O. mariannensis in Micronesia. We demonstrated different origins of the two endemic Ochrosia species on the Bonin Islands. This study provided an excellent example of the complex origins and speciation of flora in the oceanic islands.

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A new species of Lasianthus (Rubiaceae) from Kon Chu Rang Nature Reserve in central highlands of Vietnam

Dinh Hiep Nguyen, Minh Quan Dang, Ngan Thi Kim Le, Van Toan Em Quach, Van Ngot Pham, Van Tho Le, Ba Vuong Truong, Naiki Akiyo, Van-Son Dang

PHYTOTAXA ( MAGNOLIA PRESS )  541 ( 3 ) 291 - 296   2022.03 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Lasianthus kbangensis V.S.Dang, Vuong & Naiki, a new species belonging to Lasianthus sect. Nudiflorae of Rubiaceae from the Central Highlands of Vietnam, is described and illustrated. This new species is similar to L. oblongilobus H. Zhu, but differs in having larger leaves, longer petioles, smaller calyx (calyx lobes) and corolla, and the color of ripen fruits. A table comparing the new species to closely related species is provided.

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Comparisons among populations and individuals to evaluate pollen-pistil interaction as a mechanism of reproductive interference in Taraxacum

Hashimoto Keisuke, Yamamoto Akane, Kanaoka Masahiro M., Naiki Akiyo, Takakura Ko-Ichi, Nishida Sachiko

JOURNAL OF PLANT RESEARCH ( Journal of Plant Research )  135 ( 1 ) 29 - 40   2022.01 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Reproductive interference (RI), an interspecific mating interaction that reduces the fitness of at least one of the species involved, can lead to exclusive distributions in closely related species. A hypothesis previously proposed is that RI in plants may occur by ovule usurpation, in which pistils lack interspecific incompatibility and mistakenly accept heterospecific pollen, thereby losing an opportunity for conspecific pollen fertilization. However, few comparative studies have evaluated the consistency of the inferred mechanism within and among individuals and populations. We conducted hand-pollination experiments in six populations of three native Taraxacum species that suffered from different levels of RI from an alien congener, T. officinale, and compared pollen-pistil interactions among populations. We also investigated the interactions for eight individual T. japonicum plants whose response to heterospecific pollen deposition had been previously measured. Our results revealed that pollen tubes often penetrated native ovaries following heterospecific pollination in populations suffering from strong RI, whereas they seldom did in populations suffering from marginal RI. However, the relative frequency of the pollen tube penetration was not significantly related to the strength of alien RI. Not all pistils on an individual plant showed the same pollen receptivity following heterospecific pollination; rather, some accepted and some refused the pollen tubes. The relationship between pollen tube penetration following heterospecific pollination and the strength of the alien RI was also not significant among individuals. Our present results generally support the ovule usurpation hypothesis, but suggest that other factors, such as competition for pollinator services, variation in the effects of heterospecific pollen donors, and condition of the native inflorescences, might also affect the observed RI strength.

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Hydrangea marunoi (Hydrangeaceae), a new species from Osumi Peninsula, southern Japan

Tagane S., Fujii S., Hirota K., Naiki A., Yahara T.

PhytoKeys ( PhytoKeys )  211   33 - 44   2022 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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A Revision of Leptopetalum foetidum (Rubiaceae)

Akiyo Naiki, Tetsuo Ohi-Toma

The Journal of Japanese Botany   96 ( 6 ) 326 - 333   2021.12 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

The taxonomy of Dischidia ruscifolia (Apocynaceae, asclepiadoideae) and the description of a new species, dischidia argentii

Arshed M.J., Callado J. R., Tandang D., Naiki A., Agoo E. M., Rodda, M.

Taiwania ( NATL TAIWAN UNIV PRESS )  66 ( 4 ) 496 - 503   2021.11 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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We document the taxonomic history of Dischidia ruscifolia Decne ex Becc. After a critical study of the available original material and additional specimens an epitype is designated. We confirm that D. myrtillus is a synonym of Dischidia ruscifolia and the name is typified. Clarification of the identity of D. ruscifolia allowed the identification of a new species that is here published and illustrated as Dischidia argentii Arshed, J.R. Callado & Tandang. The new species differs largely in its floral morphology and particularly in its glabrous corolla throat, absent corolline corona, gynostegium outline, and pollinium shape.

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Phylogenetic Relationship of Tropical Asian Ardisia and Relatives (Primulaceae) Shows Non-monophyly of Recognized Genera and Subgenera

Julius A, J. S. Gutiérrez-Ortega, S. Sabran, S. Tagane, A. Naiki, D. Darnaedi, M. M. Aung, V. S. Dang, N. V. Ngoc, H. T. Bin, Y. Watano, T. M.A, Utteridge, T. Kajita

The Journal of Japanese Botany   96 ( 3 ) 149 - 165   2021.06 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

Morphology, phenology, and chromosomal observations in Najas minor and Najas chinensis from iriomote island, Okinawa, Japan

Kajita Y., Toyama H., Akai K., Naiki A.

Acta Phytotaxonomica et Geobotanica ( 日本植物分類学会 )  72 ( 2 ) 167 - 177   2021 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Najas minor and N. chinensis are newly reported from southern Iriomote Island, which is the southern-most distribution for both species in Japan. The morphology, reproductive phenology, and chromosomal numbers were compared with reports from previous studies. Najas minor on Iriomote Island was larger, up to 120 cm long, had longer leaves (3 to 4 cm long), flowered and fruited year-round and had a new karyotype (2n = 24) for the species in Japan. Najas chinensis on Iriomote Island was within the reported range of morphological and chromosomal variation for the species, but flowering and fruiting were observed almost throughout the years of study. Phenological and morphological descriptions provide new insights into the life cycles and identification of N. minor and N. chinensis.

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New record of alien Oldenlandia boscii (Rubiaceae) from the University of Tokyo Tanashi Forest in Japan

Tsuruta Momi, Naiki Akiyo, Lian Chunlan

The Journal of Phytogeography and Taxonomy ( Japanese Society for Plant Systematics )  69 ( 2 ) 211 - 214   2021 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Taxonomic studies on Zingiberaceae of Myanmar II: Curcuma stolonifera (Subgenus Ecomatae), a new species from the northwestern region

Tanaka N., Armstrong K., Aung M. M., Naiki A.

Brittonia ( SPRINGER )  72 ( 3 ) 268 - 272   2020.09 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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In the course of taxonomic studies on Zingiberaceae in Myanmar, a new species of Curcuma assignable to subgenus Ecomatae was discovered in Htamanthi Wildlife Sanctuary, Sagaing Region, northwestern Myanmar. It is described and illustrated here as Curcuma stolonifera. This new species differs from other species in subgenus Ecomatae Skornick. & Sida f. in having a combination of the following characters; long creeping rhizomes, an oblong-lanceolate lamina with reddish midrib, a small number of green bracts, a central inflorescence, pale whitish yellow flowers, and a short slightly L-shaped anther with a curved spur.

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Resurrection and emended description of Sciaphila major (Triuridaceae)

Kenji Suetsugu, Martin Dancak, Michal Hrones, Akiyo Naiki, Shuichiro Tagane, Tetsukazu Yahara

PHYTOTAXA ( MAGNOLIA PRESS )  459 ( 1 ) 25 - 38   2020.09 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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This paper presents a re-evaluation of the taxonomic identity of Sciaphila major described from Sarawak, Borneo, Malaysia which has been considered conspecific with S. secundiflora. We revealed that S. major is clearly distinguishable from S. secundiflora s.s. by the arrangement of flowers on rachis (spirally and subdensely arranged vs. secundly and laxly arranged), rachis length in a fully developed inflorescence [(2-)3-6(-7) cm vs. 6-19 cm], tepal length of male flowers (2-2.3 mm vs. 3-4 mm) and the number of perianth segments (more than 6 vs. 6). By spirally-arranged and white flowers, S. major is most similar to S. alba, but is distinguishable by plant height (15-25 cm vs. 25-35 cm in S. alba), rachis length in a fully developed inflorescence [(2-)3-6(-7) cm vs. 8-14 cm)], the number of flowers (usually less than 20 vs. usually more than 20), the arrangement of flowers on rachis (subdensely arranged vs. laxly arranged), the number of male perianth segments (usually more than 6 vs. usually 6) and the condition of floral disc (flat vs. bowl-shaped). We also provide an updated key to the species of Sciaphila distributed in Borneo.

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A new species of Lasianthus (Rubiaceae), L. konchurangensis, from the Central Highlands of Vietnam

Thi Dung Ha, Bui Hong Quang, The Bach Tran, Hai Van Do, Huong Nguyen Thi Thanh, Ha Bui Thu, Tagane Shuichiro, Oguri Emiko, Naiki Akiyo, Van-Son Dang

PHYTOTAXA ( Phytotaxa )  451 ( 2 ) 161 - 168   2020.07 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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A new species, Lasianthus konchurangensis V.S.Dang, T.B.Tran & T.D.Ha (sect. Lasianthus), is described and illustrated from Kon Chu Rang Nature Reserve, Gia Lai Province, the Central Highlands of Vietnam Lasianthus konchurangensis resembles L. foetidissimus but differs in having larger leaves, more secondary veins, larger calyx and purple corolla. Photographs, vernacular name, preliminary conservation assessment, and a table comparing L. konchurangensis with L. foetidissimus are provided.

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Significant loss of genetic diversity and accumulation of deleterious genetic variation in a critically endangered azalea species, Rhododendron boninense, growing on the Bonin Islands

Isagi Y., Makino T., Hamabata T., Cao P.-L., Narita S., Komaki Y., Kurita K., Naiki A., Kamenyama Y., Kondo T., Shibabayashi M.

Plant Species Biology   35 ( 3 ) 166 - 174   2020.07 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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© 2020 The Society for the Study of Species Biology Loss of genetic diversity increases the risk of extinction of a population through inbreeding depression. In addition, the number of deleterious genetic variations, which might accumulate in a small population through genetic drift, can also make the population vulnerable. Rhododendron boninense is a critically endangered azalea species, which grows on the Bonin Islands, a UNESCO World Heritage Site; its population size in the wild dropped to only a single individual. Although a governmental program for species conservation has been conducted, no successful natural regeneration or population growth was achieved. We hypothesized that the reduced genetic diversity and accumulated deleterious genetic variation might cause the vulnerability of the species, and conducted comparative genetic and genomic analyses between R. boninense and its congeners. Genetic analysis using microsatellite markers indicated that the genetic diversity of R. boninense was ultimately low; microsatellite loci of this species were all fixed, whereas the congeners maintain high allelic diversity. Based on comprehensive transcriptome analysis, the amount of deleterious variation of R. boninense was significantly greater than that of R. amanoi. Repeated generation transitions of the small population of R. boninense on the oceanic islands is likely to have resulted in low genetic diversity as well as more deleterious variations in the genome, and we speculated that the accumulated deleterious variation might result in vulnerability of R. boninense. This study indicates the possibility of evaluating the feasibility of effective conservation programs based on the genetic diversity and the amount of accumulated deleterious variation in the genome of critically endangered species.

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An Updated Phylogeny of Leptopetalum (Rubiaceae) and Taxonomic Treatment of Herbaceous Species in East Asia

Tetuo Ohi-Toma, Akiyo Naiki, Shiho Waddell, Hidetoshi Kato, Van-Son Dang, Jin Murata

The Journal of Japanese Botany   95 ( 3 ) 141 - 153   2020.06 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

Two New Species of Lasianthus (Rubiaceae) from Northern Vietnam

Dang V.S.

Annales Botanici Fennici ( Annales Botanici Fennici )  57 ( 1-3 ) 49 - 54   2020.05 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Two new species of Lasianthus (Rubiaceae). L. thuyanae V.S. Dang & Naiki from Ba Vi National Park, Ha Noi City, northern Vietnam, and L. tamdaoensis V.S. Dang from Tam Dao National Park, Vinh Phuc Province, northern Vietnam. are described and illustrated. Lasianthus thuyanae is closely related to L. curtisii but differs from it by having larger stipules and corollas, and a differently coloured calyx. Lasianthus tamdaoensis resembles L..filipes and L. longipedunculatus but differs from them by having longer petioles and larger corolla lobes.

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New Localities of Seed Plants Recorded from the Subtropical Ryukyus of Japan at Island Level Based on Herbarium Data

國府方 吾郎, 海老原 淳, 齊藤 由紀子, 天野 正晴, 阿部 篤, 中村 剛, 内貴 章世, 梶田 忠, 横田 昌嗣

Bulletin of the National Museum of Nature and Science. Series B, Botany / National Museum of Nature and Science ( National Museum of Nature and Science )  46 ( 2 ) 75 - 87   2020.05 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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The effects of water pollution on the phylogenetic community structure of aquatic plants in the East Tiaoxi River, China

Toyama H., Bessyo K., Huang L. L., Hirota S. K., Kano Y., Mase K., Sato T., Naiki A., Li J. H., Shimatani Y., Yahara T.

Freshwater Biology   65 ( 4 ) 632 - 645   2020.04 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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© 2019 John Wiley & Sons Ltd Water pollution is one of the most serious aquatic environmental problems worldwide. In China, recent agricultural and industrial development has resulted in rapid changes in aquatic ecosystems. Here, we reveal the effects of water pollution on the phylogenetic community structure of aquatic macrophytes in the Tiaoxi River, China. We placed a rectangular plot at 47 sites within the Tiaoxi River from the mouth of the river to 88.5 km upstream, in which we recorded species abundance and measured 22 physico-chemical variables. Bayesian phylogeny using the rbcL and matK gene sequences was employed to quantify phylogenetic α- and β-diversity, and test the phylogenetic signal in four growth forms: emergent, floating-leaved, free-floating, and submerged. Within communities, water contamination and phytoplankton abundance decreased species richness and phylogenetic diversity, which resulted in phylogenetic clustering; species within communities were more closely related to each other than expected. Between communities, differences in geographical distance and phytoplankton abundance resulted in phylogenetic dissimilarity among plots. Aquatic macrophytes showed phylogenetic signals in which related species responded more similarly to disturbance. Thus, the observed patterns could be explained by environmental filtering and suggested that water pollution by human activity has added more filters to the existing environmental filters that drive the species assembly of macrophyte communities.

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Habitat partitioning in native Geranium species through reproductive interference.

Nishida S, Takakura KI, Naiki A, Nishida T

Annals of botany ( Annals of Botany )  125 ( 4 ) 651 - 661   2020.03 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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BACKGROUND AND AIMS: Heterospecific pollen transfer may reduce fitness of recipient species, a phenomenon known as reproductive interference. A theoretical study has predicted that distributions of species pairs affected by reproductive interference may be syntopic under negligible reproductive interference, sympatric but with partitioning at small spatial scale (i.e., allotopic) under weak interference, or exclusive, when reproductive interference is strong. Verifying these predictions is essential for evaluation of the applicability of reproductive interference as a general assembly rule of biological communities. The aim of this study was to test these predictions in two sympatrically distributed wild Geranium species, G.thunbergii and G. wilfordii. METHODS: To measure the effect of reproductive interference, the association between the relative abundance of the counterpart species and seed set in the focal species, and seed set reduction following the mixed pollination, were analysed. The possibility of hybridization with viable offspring was examined by genotyping plants in the field and after mixed pollination. Fertility of putative hybrids was based on their seed set and the proportion of pollen grains with apertural protrusions. A transect study was conducted to examine spatial partitioning, and possible influences of environmental conditions (canopy openness and soil moisture content) on partitioning between the species were analysed. KEY RESULTS: Neither abundance of the counterpart species nor heterospecific pollen deposition significantly affected seed set in the focal species, and hybridization between species was almost symmetric. Putative hybrids had low fertility. The two species were exclusively distributed at small scale, although environmental conditions were not significantly different between them. CONCLUSIONS: The allotopy of the two species may be maintained by relatively weak reproductive interference through bidirectional hybridization. Re-evaluation of hybridization may allow ongoing or past reproductive interference to be recognized and provide insight into the distributional relationships between the interacting plants.

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Contributions to the flora of Myanmar V: A new record of Mallotus tokiae (Euphorbiaceae) with the description of flower morphology from Lampi Island

Toyama H.

Thai Forest Bulletin (Botany) ( Thai Forest Bulletin (Botany) )  48 ( 1 ) 1 - 6   2020 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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