Possible factors causing the decline of the endangered horseshoe crab species Tachypleus tridentatus were revealed by interpretation of aerial photographs, interviews with residents, and field surveys at Tsuyazaki Cove, Fukuoka, Japan. The interviews confirmed that T. tridentatus had been abundant in the area from the 1940s to the 1980s; however, the species decreased gradually and was rarely seen by the locals in the early 2000s. A field survey from 2005 to 2013 confirmed that the number of breeding horseshoe crabs had decreased dramatically over the survey period. The study results suggest that the decline in T. tridentatus can be explained by reclamation of the bay mouth. This caused poor sand supply to potential spawning sites, which in turn resulted in the degradation of the habitat of local populations of T. tridentatus. The historical ecology approaches applied here could be useful as a primary analysis tool to search for clues regarding causal relationships between the population decline of rare species and coastal development.

A project to eradicate the invasive crayfish Pacifastacus leniusculus was conducted from 2008 to 2012 at a small pond with a surface area of approximately 820 m2 in Kushiro. However, we could not eradicate it using Kanikago traps. To determine the reason, we examined the data for 2008 and classified the crayfish by body size and applied the DeLury method to each size class. A population decline was observed in large adults with carapace lengths of 4 cm or more, but not in small adults with carapace lengths of less than 4 cm. This revealed that the Kanikago traps were effective for large adults, but not small adults.

The phenology of the sexual reproduction of the tropical seagrass Enhalus acoroides (L.f.) Royle was studied at the northernmost limit of its distribution. Flowering seasons were recorded from 2013 to 2017 at Iriomote Island, Yaeyama Islands, Japan. Fruit development was monitored in 2014 and 2015. The flowering season was from May to November, when the water temperature and sunshine duration were high and the daytime low-tide level was relatively low. The timing of flowering was synchronised with the spring tides associated with lower daytime tide levels during either full or new moons. After October, the tides were high and surface-pollination failed. The average period from flowering to mature fruit dehiscence was 84±6.5 days, and was shorter than in the tropics. The pollination success (proportion of female flowers remaining after 3 days) and fruit survivorship 2 months after flowering were 51.2% and 9.8%, respectively. The proportion of fruit that matured per female flower was 9.3%. The flowering season was shorter than in tropical regions and only flowers from the earlier part of the flowering season produced seeds. This suggests that sexual reproduction is lower at the northern limit than in the tropics.

Fly infestation of wild orchids is widely recognised in Japan. The flies feed on the orchid fruit and prevent seed production. To protect orchids from fly infestation, it is necessary to identify the fly species, degree of damage to each orchid species, infested organs, and seasonal changes. This study investigated the degree of damage to four Japanese orchid species and identified the collected flies using molecular methods. We found Japanagromyza tokunagai (Sasakawa) (Diptera: Agromyzidae) on all four orchid species collected from Fukushima, Ibaraki, Chiba, and Kochi Prefectures. The fruits of Liparis nervosa (Thunb.) Lindl. and Phaius flavus (Blume) Lindl. and the flower stalks of Calanthe puberula Lindl. and Goodyera schlechtendaliana Rchb.f. were infested by the flies. The infestation of flower stalks caused deterioration of the flowers and prevented seed production in the latter two orchids. No fly damage was found on G. schlechtendaliana collected in Hokkaido Prefecture, but plants from Fukushima Prefecture were damaged, suggesting that the degree of damage differs regionally. Our results indicate that flies threaten many orchid species and that the control of J. tokunagai is an important issue for orchid conservation in Japan.

The near-endangered dragonfly Aeshna mixta soneharai mainly inhabits artificial reservoir ponds and is a natural monument protected by the regulations of Ueda, Nagano Prefecture, Japan. The habitat use of this species was investigated on the Shioda Plain, where there are many reservoir ponds. The percentage of shoreline covered by emergent water plants was higher in ponds with the dragonfly than in those without the dragonfly. In the generalised linear model, forest and apple orchard areas around the ponds positively contributed to the occurrence of this dragonfly, in addition to shoreline emergent plants. A route census at an orchard showed that A. m. soneharai used the orchard as habitat. These results are consistent with the reproductive ecology of the species, which uses emergent water plants as spawning sites. A. m. soneharai use forest habitat for sub-adult maturation. Similar to forest, sub-adult A. m. soneharai are likely to use orchards. This study suggests that restoration near reservoir ponds would be effective for the conservation of A. m. soneharai. When it is difficult to restore forest around ponds, apple orchards with economic potential might serve as an alternative habitat.

The sika deer (Cervus nippon) population on the Tanzawa Mountains increased during the 1970s. The vegetation on the mountains was strongly impacted by the intensive grazing of the burgeoning deer population. The species richness in the forest floor vegetation was dramatically reduced, and soil erosion was a frequent occurrence. In the present study, we examined the feeding preferences of the deer under prevailing conditions in the period of February.December, 2018. The preferences were determined by analysis of faecal samples. Five faecal sampling sites were chosen in the eastern (East High, East Middle), central (Mid High, Mid Middle), and western (West High) parts of the Mt. Tanzawa region. We found that (i) dicotyledonous leaves accounted for only a small proportion of the deer faeces content, (ii) fibre comprised a large proportion of the faeces, particularly in winter, and was also an important component in summer, and (iii) grasses accounted for a high proportion of faecal content at high-elevation sites. These data, together with those from other areas, suggest that the deer of this region persisted on a forage-poor diet; they were unable to access adequate quantities leafy food, even during the plant growing season. Thus, it will be important to monitor (i) the nutritional status and gestation of this deer population, and (ii) changes in vegetation components, including the populations of dwarf bamboo, for better management of the forest ecosystem on the Tanzawa Mountains.

Primula sieboldii E. Morren (Primulaceae) is an endangered species in Gifu Prefecture, Japan. There was once a wild population in Kiyomi, located in Takayama, Gifu. It is said that some individuals cultivated by people living in Kiyomi originated from the extinct Kiyomi population. In this study, we aimed to identify original genets in the Kiyomi population based on a questionnaire, a STRUCTURE analysis, and an assignment test based on DNA analysis. We detected 16 genets from 62 samples using eight SSR markers. Of the 16 genets, four (g2, g3, g4, and g6) likely originated from the Kiyomi population based on the questionnaire and their close genetic relationships. In the STRUCTURE analysis, these four genets had different genetic compositions. To examine whether the 16 genets originated from the extinct Kiyomi population, we performed an assignment test using the Takayama population, which is expected to be genetically close to the Kiyomi population. The assignment test assigned only g3 to the Takayama population, but the genet was not considered an original due to the very low probability. In conclusion, four genets were identified as likely original genets based on the questionnaire, but no positive proof was obtained from the DNA analysis following the extinction of the native population.

We developed a simplified topsoil block transplantation method to mitigate the impacts of the construction of National Route 40 on the surrounding old-growth boreal mixed-forest ecosystem of the Nakagawa Experimental Forest of Hokkaido University. Herbaceous vegetation and soil animal communities were compared between topsoil block transplantation treatments and transplantation without a blocked soil structure (controls). In the conventional method, equipment dedicated for soil blocks is used, but in our simplified method, commonly used construction machinery is used whenever possible. As a result, construction costs are dramatically reduced. The simplified soil block transplantation method developed in this study contributed to early recovery of plant and soil animal communities. Compared to control plots, block transplantation promoted higher species richness of herbaceous vegetation, composed of more native perennial herbs and woody plants and fewer exotic biennial plants. The similarity in plant communities between transplanted and source sites was greater in topsoil block plots than in control plots. The numbers of individuals and species of soil animals were also higher in topsoil block plots than in control plots. The similarity in soil animal communities between transplanted and source sites was greater in topsoil block plots compared to control plots.