The effect of self- and multiparental pollination on the seed set of endangered Aster kantoensis (Asteraceae) was examined in a hand pollination experiment. The seed set of A. kantoensis increased with the number of pollen donors, which should increase the genetic diversity of the pollen load. Based on the results of the experiment and existing information on the reproductive ecology of the species, we suggest an effective hand pollination method to aid population restoration programs using seeds and seedlings of A. kantoensis.

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The distribution, growth, survival, and germination characteristics of an annual alien plant, Ambrosia trifida, along the middle stream of the Tone River, in central Japan, were surveyed to clarify the factors that make this such an invasive species. A survey in 2000 revealed 30 large populations of the species established along the river between Meiwa (36°15' N, 139°6' E, 20 m H) on the Kanto Plain and Minakami (36°47' N, 138°59' E, 530 m H), 30 km from the source of the river. All 30 large populations were in disturbed locations, such as the sites of construction of artificial banks, bridges, gravel roads, and quarries. The biggest population, which was found in Meiwa, was estimated to consist of about 687 million plants, which would produce 1.7 billion seeds annually. A laboratory experiment suggested that the northern population produces seeds that germinate well at lower temperatures (15/7℃, day/night) and become dormant at higher temperatures (30/15℃). A field census in 2001 revealed that the northern population in Minakami had a high relative growth rate (RGR) as compared with that of the southern population in Isesaki (36°17' N, 139°9' E, 60 m H), although the plant biomass at Minakami (33.3 g in October 2001) was much lower than that at Isesaki (130.4 g) because germination was delayed by low temperatures. Plant survival and population density were always higher at Minakami (57 m^<-2> and 13%, respectively in October 2001) than at Isesaki (11 m^<-2> and 6%). Consequently, the seed production per unit population area was higher at Minakami (7,170 m^<-2> in October 2001) than at Isesaki (5,730 m^<-2>). These results indicate that this alien species is very vigorous and may invade a larger area. We strongly urge that human disturbance be prohibited in riverside areas, and that soil containing seeds should be immobilized to suppress the spread of this species.

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Changes in the macrophytic flora of 109 irrigation ponds located in the East-Harima area of Hyogo Prefecture, western Japan, have been studied for about 20 years. During this period, the populations of species that tolerate eutrophication, such as Trapa japonica, T. natans var. japonica, and Ceratophyllum demersum have remained stable, whereas those of many other species have declined drastically. The survival rate is 10-35% in species like Brasenia schreberi, Nymphaea tetragona, and many submerged species. In addition, the dominance of each species has also changed remarkably, which means that many species are on their way to extinction, and the most recent survey failed to find 4 of the 30 species recorded in the study ponds. Species diversity, as expressed by the numbers of floating-leaved, submerged, and free-floating species, has also declined. There are now five times as many irrigation ponds without vegetation as there were 20 years ago. The critical status of aquatic macrophytes revealed in this survey reflects the crisis in the biodiversity of irrigation ponds and the urgent need to conserve these habitats.

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To determine the structural changes of a tree population in an isolated stand of lucidophyllous forest, we carried out a tree census in a 0.47-ha plot in a 3.4-ha primary forest in 1989 and 2000, and analyzed the 11-year change in the stem number for canopy and subcanopy species. The stems above 1.3 m in height in the study plot were classified into three size classes: canopy, subcanopy, and sapling. For the 52 species combined, the ratio of stems in the canopy class decreased (-1.0% year1^<-1>). The dominant canopy species, Distylium racemosum, showed little change in population structure and had abundant stems in all size classes in both 1989 and 2000. The three dominant canopy Cyclobalanopsis species (Quercus salicina, Q. sessilifolia, Q. gilva) had few stems in the subcanopy class in 1989. The stem number in the canopy class of each of these three Quercus species decreased considerably (more than -1.0% year^<-1>) and there was a small decrease in the subcanopy class in 2000. For Quercus, most of the stems newly recorded in the sapling class in 2000 were sprouts from stools recorded in 1989. For the Lauraceae and Theaceae, major families in the flora of lucidophyllous forests, the populations of most canopy and subcanopy species in 2000 were the same as in 1989. Of the major canopy and subcanopy species other than Quercus species, 43-97% of the stems newly recorded in the sapling class in 2000 were main stems that were recruited via seed reproduction. The population changes observed in this study site, which in 2000 had been undisturbed for at least 40 years, suggest that the population of Quercus species will decrease in the near future, while that of the other major species will remain stable. Although no structural characteristics or population changes were regarded as due to forest fragmentation, the loss of five species from a small population in 11 years suggests that there will be a further decrease in the number of species in the study plot. The tree population and the area of isolated stands with high species diversity, such as the study plot, should be increased by disseminating species to neighboring areas before many of the species in the stand lose their ability to regenerate by active seed reproduction.

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Regional populations of two terrestrial Utricularia species were studied. Small oligotrophic spring-fed hillside marshes are the habitat of these species in the region studied. The probability that a habitat patch was occupied by a species was positively correlated with the local patch density in both species. The regional population was a metapopulation in the strict sense. The critical patch density to prevent extinction (plants appeared in 90% of habitats) was 3.4 patches within a 500-m radius in U. racemosa (4.3 km^<-2>) and 3.1 patches within a 100-m radius in U. bifida (99 km^<-2>). The number of patches within an effective spatial scale was similar (3-4 patches) despite the large difference in absolute density (4.3-99 km^<-2>). To conserve terrestrial Utricularia in this region, groups of marshes should be conserved.

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The population expansion of an invasive alien grass, Eragrostis curvula, in a gravelly floodplain of the middle reach of the Kinu River, was predicted from measured demographic traits. We applied a lattice model to our simulation, and expressed the population processes in each cell by using a stage-structured vector and projection matrix. The dormancy/germination traits revealed suggest the absence of a persistent soil seed bank. In the floodplain, the seeds germinate immediately after seed dispersal. The seed dispersal pattern was estimated from the distribution of adult plants and seedlings in a lattice survey area. The results of the simulation predict that the area dominated by E. curvula is increasing 3.31-4.14 fold annually, and that it will be occupy 50% of the area of the floodplain within less than 10 years and 100% within 12 years. To prevent E. curvula invasion from affecting endemic river plants and the riparian ecosystem, it is essential that E. curvula be removed mechanically during the early stage of invasion, while simultaneously restoring the gravelly substrate.

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We studied the optimal conservation and assessment effort for a population in a fluctuating environment. The optimal conservation effort is that required to prevent a population of animals or plants from becoming extinct in a randomly fluctuating environment; the optimal assessment effort is that necessary to reduce the uncertainty of the current population size. The optimal management strategy is that which minimizes the weighted sum of the extinction probability and the economic cost of the conservation and assessment efforts. We showed that (1) the optimal effort is greatest with a moderately large variance in the environmental noise; (2) the conservation level in the first year of a multiple-year optimization is lower than for a single-year optimization if the population is endangered; and (3) when the variance in the prior distribution of the population size is large or the environmental fluctuation is small, the optimal assessment effort is large.

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To protect native wildlife species, the Ministry of the Environment launched a program to control mongooses (Herpestes javanicus) on Amami-Oshima Island (712 km^2) in Kagoshima Prefecture. The population status was investigated for the fiscal years (FY) from 1996 to 1999; the population in 1999 was estimated to be 5,000 - 10,000 and to be increasing at an annual rate of 40%. Based on this study, an eradication attempt was planned, and a trapping campaign with a bounty was introduced in FY2000. By the end of FY2002, 9,469 individuals had been caught, and a monitoring survey indicated that the population size and density had decreased to less than half the peak seen in 1999. However, at present the population is not being reduced; the fall in trapping efficiency has led to a decline in trapping, while the range of the mongoose is spreading. It is now crucially important to intensify trapping and plan trap allocation.

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The Chugoku Electric Power Company (CEPC) plans to construct a nuclear power plant with two 137.3-megawatt reactors on Nagashima Island, near Kaminoseki, which borders the Suo-nada Sea in the western-most portion of the Seto Inland Sea National Park, Japan. The natural environment of the Seto Inland Sea, the biggest partially closed water system in Japan, has deteriorated since the 1970s due to the effects of landfilling, dredging, and industrial pollutants associated with the development of industrial complexes. Recently, it was revealed that despite this pollution the biodiversity of the Suo-nada Sea is still exceptionally well conserved. It currently has the best-conserved shallow water maritime biodiversity in Japan. The following rare or endangered species are found near the proposed site: falcons (Falco peregrinus), finless porpoises (Neophocaena phocaenoides), chordates (Branchiostoma belcheri), brachiopods (Discinisca sparselineata), and numerous new, rare, or endangered molluscan species, of which the cornirostrid Tomura cf. Yashima is particularly important. The Japanese government enacted the Environmental Impact Assessment Law in June 1999, and the proposed Kaminoseki Power Plant is the first nuclear power plant in Japan to which this new law applies. Surprisingly, the Preparatory Report published by the CEPC (April 1999) failed to include any of the above species. In March 2000, The Ecological Society of Japan expressed concern regarding the conservation of biodiversity around Nagashima, and demanded a re-assessment (March 2001). Although the Japanese government accepted the project in July 2001, it remains at a standstill owing to the many obstacles facing it, including local landowners who have not agreed to sell their land and a fishing cooperative on nearby Iwaishima Island that has refused to accept compensation for the possible loss of their fishing rights.

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In 1978, a Japanese group intentionally released a pair of domestic goats (Capra hircus) on Uotsuri-jima, in the Senkaku Islands, in southwestern Japan. The goat population increased explosively, and now exceeds 300. Consequently, negative effects on the vegetation of the island, such as the formation of bare patches, are evident. Many endemic and biogeographically important species occur on this island, and many of them are likely to go extinct in the near future if these negative effects continue. It is becoming increasingly difficult to solve this problem because of the territorial conflict over the Senkaku Islands between Japan, China, and Taiwan. The Ecological Society of Japan adopted a resolution entitled, "Appeal for the Eradication of Introduced Goats on Uotsuri-jima in the Senkaku Islands" at its business meeting at the 50th Annual Congress of the Society held in March 2003, and submitted it to the Ministries of the Environment and Foreign Affairs of Japan. Similar resolutions were adopted by The Mammalogical Society of Japan in 2002 and The Biological Society of Okinawa in 2003. How the Japanese Government will decide to respond to these resolutions is currently the focus of numerous Japanese scientists, who are especially interested in whether it will be possible to conduct research by landing on the island.

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