Misc

The population of Chimaphila umbellata, a partially mycorrhizal heterotroph, is rapidly declining in Ibaraki Prefecture, Japan, the southern limit of its global distribution, requiring urgent conservation. This study analyzed plant samples from various regions of Japan to investigate the population genetic structure and phylogeny. The results revealed that the southern population is genetically distinct from the northern one and derives from a single ancestral group. In situ seed sowing techniques in Aomori Prefecture showed no fully grown individuals, suggesting unsuitable post-germination conditions. In contrast, in situ seed sowing techniques in Ibaraki showed embryo elongation and branching, indicating a symbiotic relationship with a specific basidiomycete Serendipitaceae during growth. Analysis of the fungal community in the soil indicated that the distribution of Serendipitaceae was limited.

Chimaphila umbellata is a partially mycoheterotrophic plant, so the involvement of fungi is necessary at the time of germination. This species distributes in the northern hemisphere. In Japan they are found in Hokkaido, Aomori, Iwate, and Ibaraki prefectures. In Hitachinaka city, Ibaraki prefecture, the southern limit of the distribution, the number of individuals has dropped sharply making them in danger of extinction.In order to clarify their germination conditions in the southern limit, seed packets were buried in various environments in autumn 2018. After 6 and 10 months, recovered packets were examined and germination was confirmed. The state of the germination was in an early stage where the embryo expands and breaks the testa. It is necessary to continue the investigation in order to identify the environmental conditions suitable for symbiotic fungi and germination.Next, in order to compare the breeding status of populations in the southern and the northern (Hokkaido and Aomori prefecture) regions, we surveyed growing area in July to August 2019. As a result, it was not possible to confirm the breeding by the seedlings in all surveyed areas, but the growth density, the number of flowers and fruits were larger in the growing area in the northern part, and hence the possibility of seed breeding would be higher in these regions. In the southern limit, as major pollinator of Chimaphylla umbellata was lacked, artificial pollination is considered to be effective for better fruiting. Finally, population genetics analysis using next-generation sequencing revealed that populations in the southern limit are genetically uniform and that they have less genetic diversity than those in the north. It is necessary to take conservation measures as soon as possible in these areas.