Biology subjects

Tsunamoto, Y.

Publications and source records attributed to Tsunamoto, Y..

3 recordsLinked to original sources

bioRxiv2022

Extremely low level of genetic diversity in Gentiana yakushimensis, an endangered species in Yakushima Island, Japan

Rare or endangered species largely contributing to global biodiversity are essential components of ecosystems. Because genetic diversity depends not only on apparent population size but also demographic processes, the conservation priority of endangered species based on population genetics needs to be assessed by comparison with common congeners and demographic events. In this study, we performed population genetic analysis for Gentiana yakushimensis Makino, a rare and endangered plant species with an isolated distribution on Yakushima Island, Japan. We performed comparison of genetic diversity with the congener (Gentiana triflora Pall. var. japonica (Kusn.) H.Hara), demographic inference, and bottleneck test based on genome-wide single nucleotide polymorphisms. The result was that G. yakushimensis had an extremely low genetic diversity level and a high inbreeding coefficient level compared to those of the congener. The population of G. yakushimensis was estimated to experience an expansion during the Last Glacial Maximum and a recent bottleneck by the demographic inference and the bottleneck test. Therefore, the low level of genetic diversity of this species might have resulted from the impact of the recent bottleneck and the long-term maintenance of a small population size. Due to the long lifespan of the genus Gentiana, the current level of genetic diversity probably does not reflect a large part of recent demographic events, which requires long-term monitoring of changes in genetic diversity to identify the time lag between the reduction in apparent population size and genetic diversity as a future outlook.

genetics↗

bioRxiv2020

Timing of fruiting rather than topography determines the direction of vertical seed dispersal by mammals and birds

Vertical seed dispersal toward higher or lower altitudes has been recognized as one of the critical processes for plants to escape from climate change. Studies exploring vertical seed dispersal are scarce, preventing the prediction of future vegetation dynamics. In the present study, we show that the timing of fruiting, rather than topography, determines the direction of vertical seed dispersal by mammals and birds across mountains in central Japan. We found strong uphill seed dispersal of summer fruiting cherry and weak downhill seed dispersal of summer-to-autumn fruiting cherry, irrespective of mountains and animals. The ascent or descent of animals, following the altitudinal gradients in food plant phenology in the temperate zone, was considered to be a driver of the biased seed dispersal. We found that megafauna (i.e., bears) intensively dispersed seeds vertically. The results suggest that the timing of fruiting and megafauna strongly affect whether animal-dispersed temperate plants can maintain their populations under climate change.

ecology↗

bioRxiv2019

Serpentine mountain uplift in northern Japan triggered the divergence of a narrow endemic from a widespread (sub)arctic Asia-Alaska species complex of Lagotis (Plantaginaceae)

In the circumboreal region, plants often have extremely-wide species ranges. Lagotis minor-glauca species complex widespread from (sub)arctic Asia to Alaska, however, have two allied narrow endemics in northern Japan: a serpentine plant L. takedana endemic to the Yubari Mountains (Mt. Yubari) and a non-serpentine plant L. yesoensis endemic to the Taisetsu Mountains (Mt. Taisetsu). Elucidating their origins sheds light on drivers for secondary-speciation of widespread circumboreal plants. To infer phylogenetic distinctiveness of two narrow endemics with those related taxa, which contained 25 out of all the 29 species of the genus, chloroplast DNA (cpDNA), nuclear ribosomal (nrITS), two low copy nuclear gene (LCN) markers and genome-wide single-nucleotide polymorphism genotyping (MIG-seq) were used. In the result of cpDNA analyses, the Lagotis minor-glauca species complex formed a clade. Within the clade, L. yesoensis and a portion of L. glauca samples formed a subclade. However, monophyly of each of the four species was not supported. In the results of nrITS and two LCN analyses, L. takedana was monophyletic, while monophyly was not recovered for each L. yesoensis, L. glauca, and L. minor. Based on a Bayesian dating analysis using nrITS data, the age of the most recent common ancestor of L. takedana was Ma (95% confidence interval: 0.05-1.75 Ma). Possible scenario is that an ancestral linage being adapted to serpentine soils migrated into the alpine habitat of Mt. Yubari, that was formed with mountain uplift by the early Pleistocene, and subsequently reproductively isolated from non-serpentine populations and speciated. The contrasting result of L. yesoensis, that was phylogenetically indistinct, is possibly explained by incorrect taxonomy, or alternatively, shallow history and incomplete lineage sorting. In Mt. Taisetsu, massive volcanic eruptions had occurred the Early Pleistocene and even after the last glacial period, suggesting that alpine plants have not migrated into and established populations in Mt. Taisetsu until very recently. To fully resolve the phylogeny of the three species L. yesoensis, L. glauca, and L. minor, further analyses using high resolution molecular markers are needed. The present study illustrated that two narrow endemics in northern Japan diverged from the widespread species include phylogenetically distinctive and indistinctive species, owing to historical orogeny and ecological factors.

ecology↗