Yakushima Island Research Articles

九州本土および屋久島の植栽ゲッキツ（ミカン科）で新たに発生したハマセンダンキジラミ（半し目：キジラミ科）

The occurrence of Psylla evodiae Miyatake, which has been known to occur on Euodia meliifolia (Rutaceae) in the Yaeyama Islands of Japan and in Taiwan, has been newly recorded in Kyushu (Fukuoka, Nagasaki, and Kagoshima prefectures) and on Yakushima Island and Okinawa Island in southwestern Japan. In addition, it has been confirmed that P. evodiae feeds on Murraya paniculata (Rutaceae), which is a newly recorded host plant in southern Kyushu (Kagoshima Prefecture) and Yakushima Island. It has also been confirmed that P. evodiae feeds on Zanthoxylum beecheyanum var. alatum (Rutaceae) in Okinawa Island.

屋久島へのIターン移住における仲介不動産業者の役割

I investigated the role of a real estate agency dealing with property on Yakushima Island and the effect this has had on migration to the island. I examined the information provided and the services offered by the agency and how migrants received them. Furthermore, I looked at how migrants and local residents got on with each other. Through my research, I have clarified what the process of migration to Yakushima actually involves.

Pohlia drummondii var. drummondii found in Yakushima Island(Taxonomical and ecological notes on Asian bryophytes, 13)

Pohlia drummondii var. drummondii found in Yakushima Island(Taxonomical and ecological notes on Asian bryophytes, 13)

Nematodes from Raccoon Dogs (<i>Nyctereutes procyonoides viverrinus</i>) Introduced Recently on Yakushima Island, Japan

Nematodes were collected from 14 raccoon dogs (Nyctereutes procyonoides viverrinus) on Yakushima Island, Kagoshima Prefecture (Kyushu), Japan, that were the progeny of recently introduced animals to this World Natural Heritage Area, probably within the last 2 decades. Seven nematode species (Toxocara tanuki, Ancylostoma kusimaense, Arthrostoma miyazakiense, Strongyloides planiceps, Trichuris vulpis, Gongylonema sp., and Dirofilaria immitis) were collected from the raccoon dogs. Two nematode species (Molineus legerae and Strongyloides martis) were collected from 2 Japanese weasels (Mustela itatsi) indigenous to this island that were killed by traffic accidents. Considering that foxes and other carnivores, except for weasels, dogs and cats, are not distributed on this island, most of soil-borne nematodes such as roundworms, hookworms, and threadworms in raccoon dogs should have been introduced by the original population from the mainland Japan, and the infection hence maintained at a high level by new generations. Recovery of the third-stage larvae of Gongylonema sp. from the esophagus of raccoon dogs was remarkably frequent (79%), suggesting that the animals might vigorously take insect hosts. Although S. martis have never been recorded from weasels in Japan until this study, this threadworm might be prevalent in a variety of mustelids in Eurasia.

Assessing the risk of economic damage to crops caused by Japanese Macaques on Yakushima Island

Assessing the risk of economic damage to crops caused by Japanese Macaques on Yakushima Island

Note on Dozya japonica in Yakushima Island, the southern end of its distributional region(Taxonomical and ecological notes on Asian bryophytes, 12)

Note on Dozya japonica in Yakushima Island, the southern end of its distributional region(Taxonomical and ecological notes on Asian bryophytes, 12)

Modeling potential habitats for Lagerstroemia subcostata var. fauriei, a rare riparian species on Yakushima Island, by analysis of GIS-derived topographic factors

Modeling potential habitats for Lagerstroemia subcostata var. fauriei, a rare riparian species on Yakushima Island, by analysis of GIS-derived topographic factors

Syrrhopodon yakushimensis found in Okinawa Island and Yakushima Island, southern Japan(Threatened Bryophytes in Japan)

Syrrhopodon yakushimensis found in Okinawa Island and Yakushima Island, southern Japan(Threatened Bryophytes in Japan)

Variation in tree growth, mortality and recruitment among topographic positions in a warm temperate forest

Questions: Do the population dynamics of trees differ among topographic positions and, if so, how does topographic position affect the population dynamics of species that are distributed in a topography-specific manner? Which is the most important life stage in determining vegetation patterns? Location: Primary and secondary warm temperate evergreen broad-leaved forest (40 - 280 m a.s.l.) on the western part of Yakushima Island, Japan. Methods: Mortality, recruitment, DBH growth and distribution of stems (≥ 5 cm DBH) in a 2.62-ha plot were surveyed in 1992 and 2002 to determine the relationships between population parameters and (1) topography and (2) distribution patterns of 17 common tree species. Results: Common species (n = 17) were classified into three distribution pattern groups: group A, distributed mainly on convex slopes; group B, on concave slopes, and group C, not aggregated with respect to topographic position. Stem mortality, recruitment and DBH growth were greater in group A than in group B within each topographic class. The hierarchy of stem mortality among topographic classes for groups A and B was convex > planar > concave. Stem recruitment density was relatively high on the convex and concave slopes, respectively, for groups A and B. Conclusions: The topographical positions of adult trees were not always most suited for adult survival and growth. For group A, the distribution pattern of adults was determined in the juvenile stage, while this was not the case for group B. Studies of juvenile stages are important for understanding the demographic basis of vegetation distribution patterns.

Geographical variation in the cranial and external characters of the little tube-nosed bat,Murina silvatica in the Japanese archipelago

The distribution ofMurina silvatica (Yoshiyuki, 1983) in the Japanese archipelago extends over about 2000 km from north to south. Specimens were obtained from populations in Hokkaido and Yakushima, which are at the northern and southern ends of the range, and from two intermediate locations in Honshu. Measurements of cranial and external morphology were examined for evidence of geographical variation. The results of both multivariate analysis of variance and cluster analysis showed that there was no distinct cline in skull morphology among the Hokkaido, Tohoku and Chubu populations. However, the results of multivariate analysis of variance showed that all measures were significantly greater for the Yakushima population than for the others. Similarly, in a dendrogram of cluster analysis, the Yakushima population formed a cluster that was distinct from the other populations. However, as the difference between the Yakushima population and the other populations was less than the variation found within the Hokkaido, Tohoku and Chubu populations, morphological divergence of the Yakushima population was attributable to intraspecific variation. The island of Yakushima is the most isolated of the four locations and the morphological divergence of this population may be associated with its relative geographic isolation.

Affiliative relations among male Japanese macaques (Macaca fuscata yakui) within and outside a troop on Yakushima Island

Male Japanese macaques (Macaca fuscata yakui) in a troop on Yakushima Island frequently groom other males. However, previous studies have not compared the social relations of troop males to those of non-troop males. I followed all troop males and non-troop males in and near a troop during a mating season and during the following non-mating season and recorded their neighbors, grooming, and agonistic interactions. Comparisons of the social relations of troop males and non-troop males with other troop members revealed that grooming and agonistic interactions with females during the mating season were similar between troop and non-troop males. However, troop males groomed each other more often and had fewer agonistic interactions among themselves than did non-troop males. Compared to what occurred in the mating season, troop males groomed females less often and exchanged grooming bouts more often with other troop males during the non-mating season. One non-troop male groomed females more frequently than did any troop male in both seasons, and this male groomed troop males more frequently than did any troop male in the non-mating season. This male immigrated into the troop during the following mating season. Regardless of their competition with respect to reproduction, male Japanese macaques on Yakushima Island maintain affiliative relations, probably to cooperatively defend fertile females from non-troop males.

Sex, Rank and Age Differences in the Japanese Macaque (Macaca fuscata yakui) Participation in Inter‐Group Encounters

AbstractIn many species interactions among group are often characterized by agonistic behaviour. Although animals may participate in inter‐group encounters in different ways, depending on their energetic requirements, reproductive tactics, and/or developmental stage, the proximate causes affecting an animal's participation in inter‐group encounters are still poorly understood. Indeed, many studies have analysed the behaviour of males and females during inter‐group encounters without considering the importance of additional factors (e.g. rank). This study focuses on wild non‐provisioned Japanese macaques (Macaca fuscata yakui) living on Yakushima Island, Japan. It aims to determine how monkeys of different sex, age, and rank behave during inter‐group encounters and it discusses the implications and consequences of their behaviour on group composition and male dispersal. Males participated significantly more than females in inter‐group encounters, by displaying more aggressive or affiliative behaviour. High‐ranking and/or adult males were more aggressive than low‐ranking and/or subadult males during encounters occurring in the mating season and they also showed more herding behaviour. This trend was not found in inter‐group encounters occurring during the non‐mating season. Finally, males which then emigrated to new groups were low‐ranking and/or subadult individuals. Those males displayed more affiliative behaviour towards foreign males than males which did emigrate. These data indicate that in non‐territorial species with male dominance over female and high competition for mating partners males play an active, and often aggressive, role during inter‐group encounter while female participation is scarce. Factors such as age, rank and period of the year (in seasonally breeding species) have to be taken into considerations when analysing interactions between groups and their effects on group composition and social behaviour.

Postconflict Behavior Among Male Japanese Macaques

Reconciliation was first described more than 20 years ago. Since then, it has been observed in many mammals (mainly primates) but data on postconflict behavior among males are still scarce because they usually aggressively compete for mating partners, rarely maintain amicable relationships with one another. Accordingly, reconciliation is expected to occur at low rates. Although this is true for Japanese macaque males, the subspecies on Yakushima Island (Macaca fuscata yakui) seems to represent an exception as grooming among males occurs often. We analyzed postconflict behavior among them and discuss the possible factors that may favor the occurrence of grooming and reconciliation. Selective attraction between former opponents—reconciliation—occurred soon after conflicts. Consolation—affiliative interactions between a focal animal and group members other than the former opponents occurring earlier in PCs than in MCs—was absent among males. Conciliatory tendency is higher for Yakushima macaque males (0.31) versus that in studies on the other subspecies Macaca fuscata. We discuss differences in the behavioral ecology of the 2 subspecies, the ecological and social factors that may favor the occurrence of reconciliation, and the possible benefits that males gain from grooming exchange and reconciliation.

屋久島西部海岸地域における絞め殺し植物（アコウ、イチジク属）の分布と地形要因の関係

屋久島西部海岸地域における絞め殺し植物（アコウ、イチジク属）の分布と地形要因の関係

Molecular variation of Spiranthes sinensis (Orchidaceae) in Japan, with special reference to systematic treatment of seasonally differentiated groups and a dwarf form, f. gracilis, from Yakushima Island

Molecular variations of Spiranthes sinensis Ames var. australis (R.Br.) H. Hara et Kitam. ex Kitam. in Japan were examined to evaluate the validity of the seasonally differentiated groups and a dwarf form of the species, which is endemic to Yakushima Island, Japan. Sequence differences in the plastid trnL-F locus clearly distinguished Japanese S. sinensis var. australis from S. sinensis var. sinensis collected from Ryukyu. In contrast, the trnL-F sequence of S. sinensis var. australis from Sabah, Malaysia, clearly differed from that of Japanese S. sinensis var. australis, suggesting genetic heterogeneity of Spiranthes sinensis var. australis in Asia. Moreover, a molecular analysis based on the sequences of nuclear ITS1 regions indicated that there are two major groups of S. sinensis var. australis in Japan, with a geographic distribution boundary on Kyushu Island. However, the trnL-F and ITS1 sequences did not support the genetic differentiation of the seasonally differentiated groups or the dwarf form from the other Japanese individuals. Based on these molecular data, the systematic treatment of physiological and morphological variations in the Japanese population of S. sinensis. var. australis is discussed.

Chronological trends in trace metals recorded by a tree bark pocket in Yakushima Island, Japan

Bark included within the trunk of a 200-year-old Japanese cedar tree harvested in Yakushima Island, Japan, a World Natural Heritage Site located 150 km south of mainland Japan and 800 km east of Shanghai, China, was analysed for trace metals by ICP-MS providing a chronology of atmospheric pollution. The concentration of V, As and Pb in decadal sections of the bark pocket increased 30 to 50 fold from 1900-09 to 1960-69, indicating increased atmospheric deposition of these metals. The trend coincided with the establishment and expansion of heavy industries in Kyushu, Japan, resulting in locally high levels of air pollution. V, As and Pb subsequently declined, reflecting lower industrial emissions following air pollution control legislation from the late 1960's and decline in heavy industries. Ni, Cu and Zn showed a relatively small, 7 to 10 fold increase over time. Lead isotope ratios in the bark pockets shifted from about 0.84 to 0.86 for 207Pb/206Pb and from 2.04 to 2.10 for 208Pb/206Pb, showing that the origin of atmospheric lead changed over time from coal to more diverse sources.

Species composition and environments of riparian forests consisting of Lagerstroemia subcostata var. fauriei, an endangered species on Yakushima Island

Species composition and environments of riparian forests consisting of Lagerstroemia subcostata var. fauriei, an endangered species on Yakushima Island

Geographical host change in the kleptoparasitic spider Argyrodes kumadai associated with distribution of two host species

We examined host utilization pattern of the kleptoparasitic spider Argyrodes kumadai along a geographical gradient from central Japan to southwest Islands. Host species changed abruptly between Yakushima Island and Amami-oshima Island: Agelena silvatica (Agelenidae) in northern regions and Cyrtophora moluccensis (Araneidae) in southern regions. This is the first report showing allopatric host change in kleptoparasitic spiders.

Floral and Ecological Features of Eriocaulon atrum Nakai and Its Close-Allies in Yakushima Island, Southern Japan

Floral and Ecological Features of <i>Eriocaulon atrum</i> Nakai and Its Close-Allies in Yakushima Island, Southern Japan

名水を訪ねて(69)屋久島の名水

名水を訪ねて(69)屋久島の名水