Genetic consequences of Last Glacial-Holocene changes in snowfall regime in Arnica mallotopus populations: A plant confined to heavy-snow areas of Japan.

PREMISE: Snow is an important environmental factor affecting plant distribution. Past changes in snowfall regimes may have controlled the demographies of snow-dependent plants. However, our knowledge of changes in the distribution and demographies of such plants is limited because of the lack of fossil records. METHODS: Population genetic and landscape genetic analyses were used to investigate the response of population dynamics of Arnica mallotopus (Asteraceae)-a plant confined to heavy-snow areas of Japan-to changes in snowfall regimes from the Last Glacial Period to the Holocene. RESULTS: The population genetic analysis suggested that the four geographic lineages diverged during the Last Glacial Period. The interaction between reduced snowfall and lower temperatures during this period likely triggered population isolation in separate refugia. Subpopulation differentiation in the northern group was lower than in the southern group. Our ecological niche model predicted that the current distribution was patchy in the southern region; that is, the populations were isolated by topologically flat and climatically unsuitable lowlands. The landscape genetic analysis suggested that areas with little snowfall acted as barriers to the Holocene expansion of species distribution and continued limiting gene flow between local populations. CONCLUSIONS: These findings indicate that postglacial population responses vary among regions and are controlled by environmental and geographic factors. Thus, changes in snowfall regime played a major role in shaping the distribution and genetic structure of the snow-dependent plant.

Genetic purity of a rear-edge population of Carex podogyna Franch. et Sav. (Cyperaceae) maintained under interspecific hybridization.

Interspecific hybridization is a critical issue in conservation biology because it may drive small populations to extinction through direct or indirect processes. In this study, to develop a conservation strategy for an endangered rear-edge population of Carex podogyna in Ashiu, Kyoto, Japan, we performed a molecular genetic analysis of the wild population and an ex-situ population established from wild seeds. Microsatellite genotypic data revealed a complete loss of genetic diversity in the wild population, suggesting that it has long been prone to genetic drift due to isolation as a small population. In contrast, microsatellite analysis of 13 ex-situ individuals detected multiple alleles that are not harbored in the wild C. podogyna population. Sequence analysis revealed that these individuals are likely natural hybrids between C. podogyna and a co-occurring species, C. curvicollis, although established hybrids have never been found in the natural habitat. Based on our observation of variegated leaves in hybrid individuals, we propose that hybrids have been excluded by natural selection and/or interspecific competition caused by insufficient productivity of photosynthesis, although other genetic and ecological factors may also be influential. Overall, this study indicates that natural mechanisms selectively removing the hybrids have maintained the genetic purity of this rear-edge population of C. podogyna, and also emphasizes the importance of genetic assessment in ex-situ conservation programs.

Identification of management units in threatened populations of Arnica mallotopus Makino (Asteraceae) using novel EST-SSR markers.

Arnica mallotopus is a perennial herb endemic to the snowy regions of Japan. At the southern edge of its distribution, in Kyoto Prefecture, overgrazing by sika deer and decreased snowfall have resulted in the rapid decline of A. mallotopus populations. Therefore, there is an urgent need for a conservation genetic analysis of the remaining local populations. In this study, we first developed 13 EST-SSR markers to evaluate genetic variation in A. mallotopus. The average number of alleles per locus was 5.33. Genetic analysis using these markers showed that the investigated samples were classified into two groups corresponding to landscape structure. One group isolated from a tributary of the Yura River showed a strong population bottleneck signal, likely resulting from founder effects and subsequent drifts. On the other hand, the genetic diversity of the second group in the main distribution along the Yura River was higher and less inbred. Overall, our assessment suggested recognizing the two genetic groups as management units in conservation programs for the threatened populations.

Seasonal and annual fluctuations of deer populations estimated by a Bayesian state-space model.

Deer overabundance is a contributing factor in the degradation of plant communities and ecosystems worldwide. The management and conservation of the deer-affected ecosystems requires us to urgently grasp deer population trends and to identify the factors that affect them. In this study, we developed a Bayesian state-space model to estimate the population dynamics of sika deer (Cervus nippon) in a cool-temperate forest in Japan, where wolves (Canis lupus hodophilax) are extinct. The model was based on field data collected from block count surveys, road count surveys by vehicles, mortality surveys during the winter, and nuisance control for 12 years (2007-2018). We clarified the seasonal and annual fluctuation of the deer population. We found a peak of deer abundance (2010) over 12 years. In 2011 the estimated deer abundance decreased drastically and has remained at a low level then. The deer abundance gradually increased from April to December during 2013-2018. The seasonal fluctuation we detected could reflect the seasonal migration pattern of deer and the population recruitment through fawn births in early summer. In our model, snowfall accumulation, which can be a lethal factor for deer, may have slightly affected their mortality during the winter. Although we could not detect a direct effect of snow on population dynamics, snowfall decrease due to global warming may decelerate the winter migration of deer; subsequently, deer staying on-site may intensively forage evergreen perennial plants during the winter season. The nuisance control affected population dynamics. Even in wildlife protection areas and national parks where hunting is regulated, nuisance control could be effective in buffering the effect of deer browsing on forest ecosystems.