Papers by Masatsugu Yokota
Journal of Japanese Botany, Dec 1, 2003
The Ryukyus Archipelago consists of about 200 nearly subtropical islands located between Japan pr... more The Ryukyus Archipelago consists of about 200 nearly subtropical islands located between Japan proper and Taiwan. Previous studies have found the Ryukyus to be a region of high biodiversity with many endangered vascular plant taxa, but they are not comprehensive. Here, we discuss the phytogeographic features and circumstances of the endangered plant taxa, make suggestions for effective in situ conservation, and highlight endangered plants in the Ryukyus that require further study.
Bulletin of the National Museum of Nature and Science. Series B. Botany, 2011
Chromosome science, Apr 1, 2004
Bulletin of the National Museum of Nature and Science. Series B. Botany, 2016
Genes & Genetic Systems, Apr 1, 2019
We developed 10 microsatellite markers for Plagiogyria koidzumii, a critically endangered fern sp... more We developed 10 microsatellite markers for Plagiogyria koidzumii, a critically endangered fern species found on Iriomotejima Island in the Ryukyu Archipelago, Japan and in Taiwan. These markers showed polymorphism among 65 wild individuals from Iriomotejima Island; the number of alleles per locus was 2-14, and mean observed and expected heterozygosity in the largest population were 0.276 and 0.277, respectively. A genetic structure analysis using these markers indicated clear genetic differentiation even within the narrow geographic range (ca. 10 × 8 km) on Iriomotejima Island. These microsatellite markers should be valuable for measuring genetic diversity and comparing genetic structure within and between populations.
Conservation Genetics, Sep 4, 2015
The population genetic patterns of a species at its range limits have important implications for ... more The population genetic patterns of a species at its range limits have important implications for species conservation. Geographically marginal populations are expected to have lower genetic diversity and higher genetic differentiation than geographically central populations. Nypa fruticans is a mangrove palm which is widely distributed from tropical to subtropical zone of Southeast Asia and Oceania. For N. fruticans, Iriomote Island in Japan represents the most northern limit of the distribution of the species. We examined the genetic variation based on 11 microsatellite markers from all 137 known ramets of N. fruticans on Iriomote Island in comparison with the more central population. Adult ramets on Iriomote Island were composed entirely of one multilocus genotype in each population and had no genetic diversity within the populations. The formation of each population by vegetative propagation from only one immigrant individual was considered to be the method of reproduction. In addition, the new juvenile which were found on the opposite side of the island possessed different alleles from other ramets in the island. This indicates that the transfer of a new genotype from another location abroad can take place. The analyses provided useful information for the continued monitoring of the demography and genetic status of these populations.
Plants, Nov 8, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Bulletin of the National Museum of Nature and Science. Series B. Botany, May 1, 2015
Tropics, 2009
The floristic composition, woody species diversity, and spatial distribution of trees in a subtro... more The floristic composition, woody species diversity, and spatial distribution of trees in a subtropical evergreen broadleaf forest on Ishigaki I s l a n d , J a p a n , w e r e i n v e s t i g a t e d b a s e d o n architectural stratification. Five architectural layers made up the forest stand. The floristic composition was almost similar between the third and the bottom layers, whereas it was almost exclusive between the top and the lower four layers. The fourth layer contained the highest potential number o f s p e c i e s (9 0). C a s t a n o p s i s s i e b o l d i i , Daphniphyllum teijmannii, Neolitsea aciculata, and Distylium racemosum were typical facultative shade species that appeared in all layers. Ar disia quinquegona was the most dominant species, as it had the highest importance value at the stand level; it was also considered a small climax species because of its disappearance in the top layer but higher importance value in the lower four layers. The values of Shannon s index H' and Pielou s index J' were 4.36 bit and 0.69, respectively, for the entire stand; these values tended to increase from the bottom layer upward, except for the H'-value of the top layer. Furthermore, woody species diversity was higher in the upper strata than the lower strata. The spatial distribution of trees was random in each layer, except in the bottom layer where trees were aggregately distributed. The degree of overlap in tree habitats differed among layers, and the results suggested that trees in the second layer could capture moderate light, while light could not easily penetrate the lower three layers. Therefore, most species in the lower layers must be shade-tolerant. The mean tree weight of each layer decreased from the top layer to the bottom layer, whereas the c o r r e s p o n d i n g t r e e d e n s i t y i n c r e a s e d. We concluded that this trend might be a general phenomenon in subtropical evergreen broadleaf for ests of the R yukyu Ar chipelago, an d we designated this trend as the quasi mean tree weightdensity trajector y of forest stratification. The relationship of mean tree height to tree density for the upper two layers supported Yamakura s quasi-3/2 power law system.
Pilea brevicornuta Hayata (Urticaceae) is a perennial herb with stolons, widely distributed in th... more Pilea brevicornuta Hayata (Urticaceae) is a perennial herb with stolons, widely distributed in the Ryukyu Archipelago and Taiwan. As contrasted with its extensive morphological variations, almost all individuals of Pilea brevicornuta had uniformly 2n=24 chromosomes except of individuals with 2n=36 from a locality on Okinawajima Island. As ba sic chromosome number of the genus Pilea is reported to be X=12, 2n=24 and 2n=36 chromosomes are regarded as diploid and triploid respectively. Triploid individuals of this speci es are reported for the first time. INTRODUCTION The Ryukyu Archipelago comprises approximately 200 subtropical islands extending southwestward from the southern Japanese island of Kyushu to northeastern Taiwan. More than 1600 vascular plants, including a number of endemics or taxa of phytogeographical interest are distributed in this chain of Japanese islands [1-3]. Morphological features of Pilea brevicornuta were fluctuating among the Ryukyu Islands and Taiwan. This widely variable species was divided into four different species based on morphological characters, but later considered as single species having high morphological variation. It prefers moist forest edges, forest floor and small ravines with high humidity. Japanese name of this plant is Shima-Mizu (island Pilea) or Arisan-Mizu. Four related taxa of Pilea brevicornuta has been known in the Ryukyu Archipelago named as P. brevicornuta Hayata from Mt. Arisan [4], P. cuneatifolia Yamamoto from Yaeyama and Amamioshima [5], P. minor Yamamoto from Remugan, Amamiohshima [5] and P. amamiana Ohwi from Amamiohshima [6]. Later on, Hatusima [7] considered Pilea brevicornuta to be an extremely variable species and suggested all the three as synonym of Pilea brevicornuta. This opinion was supported by Walker [8]. Further morphological, cytological and molecular information is needed to revise its taxonomic treatment. Kanemoto [9] reported chromosome number of 2n=24 in Pilea brevicornuta. We further investigated the chromosome number of Pilea brevicornuta in samples from an entire distribution area of this species.
Uploads
Papers by Masatsugu Yokota